Is it true that people in the Middle Ages often hydrated with beer instead of water due to clean water not always being readily available? Read this on a few places online including this one:
https://history.howstuffworks.com/medieval-people-drink-beer-water.htm
I'm afraid your question rests on a false premise. Medieval water cleanliness was Serious Business, and the notion that they all drank alcoholic drinks to make water safe is pop-cultural nonsense.
I shall direct you first to the VFAQ (Middle Ages, subsection Health and Hygiene, in case your browser doesn't go there immediately), in particular the answers from u/sunagainstgold and u/Qweniden.
To illustrate just how Serious Business water was for the Medieval era, more u/sunagainstgold on the incidents she touches on in her VFAQ post:
This is a common myth that gets thrown around a lot, in fact it's buried deep in the FAQ under hygiene and healthy lifestyles with an answer by /u/Qweniden here https://www.reddit.com/r/AskHistorians/comments/2bewpo/what_factors_made_beer_so_important_to_the/