Since people in the old times drank wine, ale and beer to quench their thirst and alcohol is considered haram in Islam, what did Early Muslims drink?

Since people in the old times drank wine, ale and beer to quench their thirst

I'm afraid you're starting from a pop-cultural myth here! I commend to your attention my main post on this matter; should you have any further questions, please don't hesitate to ask them!

Also addressing the MENA region specifically, here's a user who no longer wishes to be tagged with a post re water sources.

and alcohol is considered haram in Islam

While there is indeed a forbiddance against alcohol, I should note that what Islam says and what Muslims do are related, but they're also two separate things. Put another way, do all Christians keep the Sabbath day holy, honour their parents, do not kill, do not steal, do not commit adultery? There is most definitely a Muslim drinking culture, as you will see from the following posts:

u/Kiviimar examines the condemnation on alcohol and how well that worked out;
u/AdmiralAkbar1 considers the debate around alcohol in Islam;
u/khowaga looks at drinking laws in Iran around 1050-1100, dealing with the general attitude along the way, and also has some extra general comments here;
and Dr Omar Foda did an AMA with us, covering Egypt and its beer culture.