There certainly did exist an Islamic underworld which offered access to forbidden fruits, though few if any of our sources for it date to this early in the Muslim period. If we move a couple of hundred years later, however, we can begin to find references to a company of rogues and criminals known as the Banu Sasan in a scattering of Islamic texts from maqamat (popular) literature.

One of the best known was Abu Dulaf al-Khazraji, a self-proclaimed king of vagabonds more often noted as the author of a text apparently describing a 10th century Samanid embassy to China, who secured a tenuous position among the entourage of a vizier of Isfahan, Ibn Abbad, by telling sordid, titillating, tales of the underworld.

“I am of the company of beggar lords,” Abu Dulaf boasts in one account,

The cofraternity of the outstanding ones,

One of the Banu Sasan…

And the sweetest way of life we have experienced

Is one spent in sexual indulgence and wine drinking.

For we are the lads, the only lads who really matter, on land and sea.

Of course, that reads better in the original Persian...

Our sources are united in suggesting that a large proportion of the Banu Sasan were Kurds, a people seen by other Middle Eastern peoples as brigands and predators. They also show that the criminal slang they employed drew on a wide variety of languages. Much of it has its origins in what Johann Fück has termed “Middle Arabic,” but the remainder seems to be derived from everything from Byzantine Greek to Persian, Hebrew and Syriac.

Ultimately, however, what strikes one most about the Banu Sasan is their remarkable inclusiveness. At one extreme lie the men of violence; ar-Raghib al-Isfahani lists five separate categories of thug, from the housebreaker to out-and-out killers such as the sahib ba’j, the “disemboweler and ripper-open of bellies,” and the sahib radkh, the “crusher and pounder” who accompanies lone travellers on their journeys and then, when his victim has prostrated himself in prayer, “creeps up and hits him simultaneously over the head with two smooth stones.” But at the other lie the poets, among them the mysterious Al-Ukbari—of whom we are told little more than that he was “the poet of rogues, their elegant exponent and the wittiest of them all.”

Sadly, from the point of view of this query, the majority of the literature dealing with the Banu Sasen (most importantly the Kashf al-asrar, an obscure work by the Syrian writer Jaubari that dates to around 1235, and translates as Unveiling of Secrets) is fairly practical, and is devoted to setting out the various (often quite remarkable) crimes they committed, so that the reader could avoid being rooked by them – not to the details of their debauches. If this sort of thing is of any interest, I wrote about it in considerable detail (with more sources), here.

Ok, two things first: To answer this I fear I have to cheat a little and extent the time period that you’re asking about by a few decades into the time of the Umayyad Caliphate. I think we simply don’t really have enough information about the earliest times of the Caliphate under the rule of the Rashidun to paint a lively picture. This also moves the geographical area away from Medina and the Hejaz to the north into the steppes of Greater Syria from where the Umayyad clan ruled their continent spanning empire.

Second, I think I may have a bit of a surprise for you when it comes to the attitudes people in the early Caliphate had towards the drinking of whine and debauchery as a hole. When modern people, muslim and non muslim alike, think about the early times of the Caliphate they normally imagine a society that is tightly regulated by the norms of the Sharia. However although those norms certainly are based on guidelines that were already laid down in the times of the Prophet and the Rashidun Caliphs they weren’t really codified into law yet so to speak. Back then the formative years of islamic law that saw the establishment of the great law schools of the Hanfis, Malikis, Shafi’i`s and Hanbalis lay still in the future. That means when it came to the question whether it was allowed to drink alcohol or not all that early Muslims had to guide them were the verses of the Quran and the remembered attitudes of Mohammed. And those could be quite contradictory. Some verses are quite clear in their condemnation of alcohol:

O ye who believe! Strong drink and games of chance and idols and divining arrows are only an infamy of Satan's handiwork. Leave it aside in order that ye may succeed. (5,90)

But then another verse has this to say:

O ye who believe! Draw not near unto prayer when ye are drunken, till ye know that which ye utter, nor when ye are polluted, save when journeying upon the road, till ye have bathed. (4,43)

Here it seems that drunkenness isn’t totally forbidden or it wouldn’t be necessary to clarify that you can’t be drunken when you want to pray. Another verse even seems to praise the drinking of wine:

And of the fruits of the date-palm, and grapes, whence ye derive strong drink and (also) good nourishment. Lo! therein is indeed a portent for people who have sense. (6,67)

Now as I said, in later times those contradictory comments would be translated into a more (although still not totally) coherent set of laws by the great islamic law schools. But we would be wise not to project those later attitudes on earlier times. So while the drinking of alcohol was certainly frowned upon by more rigorous characters it wasn’t necessarily forbidden in Umayyad times.

With that out of the way we can turn to the Umayyads themselves. They were the family that monopolized the office of the Caliphate for themselves from the end of the Rashidun until they were overthrown by a rival dynasty, the Abbasids, in 750 AD. Under their rule the center of the Caliphate shifted from the Hejaz to Syria in the north where they already had been able to build a strong power base. Here they developed a sophisticated court culture that mixed elements from pre islamic Arabia with those from the Late Antique Roman and Persian Empires which they had recently conquered. The most striking witnesses to this new elite culture were the so called ‘desert palaces’ which the members of the Umayyad aristocracy build in the steppes of Greater Syria. Their still impressive ruins can today be visited in the modern states of Syria, Libanon, Jordan and the Palestinian territories.

One example from Jordan would be small palace of Qusayr Amra in modern Jordan. It is relatively modest in size but contains a really marvelous set of frescoes. The main building seems to combine the function of throne room and bath house. In it we find scenes that are familiar from Late Roman and Persian court culture like hunting scenes or a ruler on his throne. And as is fitting for a bath house we also see quite a few nude figures, most of them women. Similar depictions are known from other desert castles like this stucco statue from Khirbat al Mafjar in Palestine. It’s probably safe to assume that they’re more or less representative of the real debauchery that could be found in those aristocratic palaces.

Literary sources that tell about the Umayyads often seem to confirm this picture. In his book Walid and his friends. An Umayyad Tragedy (1988) Robert Hamilton relates a story from the Khitab al Aghani (book of songs) from the 10th century about the poet Abu Harun Utarrad who is invited to the palace of Caliph Al Walid II. He is summoned to the bath house where the ruler awaits him sitting at the edge of a bathtub filled with wine. The Caliph listens to the poet’s songs and afterward he strips off his precious garment, climbs into the tub and doesn’t come out of it until the level of wine is lowered significantly. After leaving the tub he immediately passes out so that the poet is able to steal away with the Caliph’s garment. The same scene repeats at the next evening but at the third day the poet is instead summoned to the throne room. Al Walid tells him that he can leave the palace and go his merry way but only under the condition that he will never tell anybody what he has witnessed here. Luckily for the poet only a few years later the Umayyad dynasty would be overthrown by the Abbasids so that he could freely talk about his experience.

Now stories like this should certainly be taken with more than a grain of salt. After all it was probably quite fashionable to discredit the Umayyads for their sinful lifestyle after the dynasty had lost power and their adversaries had taken control over the Caliphate. But the sumptuous decoration of the Desert Castles strongly implies that they were at least partially based in truth. And not all members of the Umayyad family seem to have been as fond of wine as Al Walid may have been, who earned a reputation as an almost legendary drunkard. His uncle and predecessor Hisham reportedly abstained from drinking wine at all and even scolded his nephew for his debauchery. But then again Hisham himself was also quite famously fond of women and music.

So we can certainly say that for a member of the Arab elite there were quite a few avenues for vice and wanton pleasure to be had in early islamic times. But they weren’t at all restricted to a glitzy underworld but an integral feature of the court culture of the time. And although I’m not at all an expert on the later islamic Middle Ages I know of a few depictions of later muslim rulers drinking wine that seem to strongly suggest that the Umayyads weren’t the last ones to live this kind of life.

Thanks to /u/mikedash and /u/Guckfuchs for the answers. I've got a follow up/related question here: