Which ones? Classical Greek Slaves, American Slaves, Ancient Egyptian slaves, Mongolian Slaves?
The task system in the Carolina low country encouraged enslaved laborers to grow corn, yams, and gourds in addition to keeping hogs, chickens, and cows. Certain plantation owners allowed their enslaved workers to travel up to 20 miles on Sundays, an accustomed free day, to sell surplus produce in urban marketplaces.
Sources: Philip Morgan, “Work and Culture: The Task System and the World of Lowcountry Blacks, 1700 to 1880,” The William and Mary Quarterly 39, no. 4 (1982): 565; Genovese, Roll, Jordan, Roll, 1-7, 535-540; Douglas R. Egerton, “Markets Without a Market Revolution: Southern Planters and Capitalism,” Journal of the Early Republic 24 (2004): 212.
Slavery is a broad topic, but I have knowledge of slavery in Virginia around the turn of the 19th century. Slaves in the commonwealth during this time period usually got Sundays off and lightened workloads during holiday seasons (a few days around Christmas and sometimes a few days around Easter). Alcohol and larger amounts of food would have been provided by their master in most instances as well. However, a master would only allow his slaves such liberties with the hope that they would be less likely to revolt and increase production. There are many excellent works on the nuances of slavery. My post is supported by my favorite one: The Internal Enemy: Slavery and War in Virginia, 1772-1832 By Alan Taylor
But you should also check out:
The Civil War of 1812 also by Alan Taylor
The Slaves Gamble by Gene Alan Smith
However anecdotal it might be, in Narrative of the Life of Frederick Douglass the author describes that the slaves did indeed get Sundays off, as well as the week between Christmas and New Year. Douglass uses Sunday afternoons to teach others to read, and describes the winter holiday as a sort of conflict between the enslaved people's will to improve their material situation and the slavers will to provide their slaves with enough whiskey to keep them drunk and docile.
I'm going to copy paste one of my old answers with what Frederick Douglas had to say about the subject.
Frederick Douglass records in his account that on some plantations slaves were not forced to work around Christmas. He felt that this was a sort of safety valve used by the slave owners to release built up tension. Nothing altruistic about it. It was unlikely to have been a practice employed by all owners, but some slaves appear to in fact have had some time to themselves. It was not for their benefit though. Here are the relevant passages.
My term of actual service to Mr. Edward Covey ended on Christmas day, 1833. The days between Christmas and New Year's day are allowed as holidays; and, accordingly, we were not required to perform any labor, more than to feed and take care of the stock. This time we regarded as our own, by the grace of our masters; and we therefore used or abused it nearly as we pleased. Those of us who had families at a distance, were generally allowed to spend the whole six days in their society. This time, however, was spent in various ways. The staid, sober, thinking and industrious ones of our number would employ themselves in making corn-brooms, mats, horse-collars, and baskets; and another class of us would spend the time in hunting opossums, hares, and coons. But by far the larger part engaged in such sports and merriments as playing ball, wrestling, running foot-races, fiddling, dancing, and drinking whisky; and this latter mode of spending the time was by far the most agreeable to the feelings of our masters. A slave who would work during the holidays was considered by our masters as scarcely deserving them. He was regarded as one who rejected the favor of his master. It was deemed a disgrace not to get drunk at Christmas; and he was regarded as lazy indeed, who had not provided himself with the necessary means, during the year, to get whisky enough to last him through Christmas.
From what I know of the effect of these holidays upon the slave, I believe them to be among the most effective means in the hands of the slaveholder in keeping down the spirit of insurrection. Were the slaveholders at once to abandon this practice, I have not the slightest doubt it would lead to an immediate insurrection among the slaves. These holidays serve as conductors, or safety-valves, to carry off the rebellious spirit of enslaved humanity. But for these, the slave would be forced up to the wildest desperation; and woe betide the slaveholder, the day he ventures to remove or hinder the operation of those conductors! I warn him that, in such an event, a spirit will go forth in their midst, more to be dreaded than the most appalling earthquake.
The holidays are part and parcel of the gross fraud, wrong, and inhumanity of slavery. They are professedly a custom established by the benevolence of the slaveholders; but I undertake to say, it is the result of selfishness, and one of the grossest frauds committed upon the down-trodden slave. They do not give the slaves this time because they would not like to have their work during its continuance, but because they know it would be unsafe to deprive them of it. This will be seen by the fact, that the slaveholders like to have their slaves spend those days just in such a manner as to make them as glad of their ending as of their beginning. Their object seems to be, to disgust their slaves with freedom, by plunging them into the lowest depths of dissipation. For instance, the slaveholders not only like to see the slave drink of his own accord, but will adopt various plans to make him drunk. One plan is, to make bets on their slaves, as to who can drink the most whisky without getting drunk; and in this way they succeed in getting whole multitudes to drink to excess. Thus, when the slave asks for virtuous freedom, the cunning slaveholder, knowing his ignorance, cheats him with a dose of vicious dissipation, artfully labelled with the name of liberty. The most of us used to drink it down, and the result was just what might be supposed; many of us were led to think that there was little to choose between liberty and slavery. We felt, and very properly too, that we had almost as well be slaves to man as to rum. So, when the holidays ended, we staggered up from the filth of our wallowing, took a long breath, and marched to the field,—feeling, upon the whole, rather glad to go, from what our master had deceived us into a belief was freedom, back to the arms of slavery.