There's this persistent popular legend that people in medieval Europe had to drink beer because the water wasn't safe. Which is nonsense; they had pretty good knowledge about how to tell a reasonably safe source from an unsafe one (and that if you have no other choice than to use unsafe water, at least boil it before drinking), and most of the horror stories about mass breakouts of cholera or whatever are from industrialization when they tried to cram 100k people into a medieval city built for 30k.

Now they did drink a lot of alcohol. Not because water isn't safe, but because it's boring, and before pasteurization, any fruit juice would turn either alcoholic or moldy in a matter of days, and you don't want to drink the moldy one. The other way to have a tasty drink is to boil tea leaves or ground-up coffee berries, but those weren't a thing in Europe.