Concerning the topic of what people were drinking in olden days.

First thing you must accept is that there are no hard answers - literally no one bothered to write this sort of thing down. The most we have are bills from large celebrations, like royal weddings, or just religious celebrations in cities. These are, as you can imagine, not exactly representative of day to day life. Another source would be expenses for a militaryt campaign, but logistics were handled in large part by requisitioning the supplies nearby, so the information there is also incomplete.

1) Water

We know for a fact that a clean source of water was a big deal. Apart from laws and regulations concerning wells, the fact that many villages sprung up around sources of water (sometimes rivers and streams, sometimes springs) is very telling. People were likely reasonably aware of the fact that the larger the water source is, the less clean it will be - a river downstream is a bad idea for drinking water, mountain stream is a lot safer (marmot piss aside). At times, you were forced to use that for drinking, but those were desperation measures.

One thing that is often forgotten is that medieval or not, people knew to boil water to make it safe. Where you run into problems is knowing when to use it - since theory of disease spreading wasn't up to snuff, boiling, filtering and, later, distilling were only used to make a water that looked unclean safer. If they knew that water will give you runs by the means of trial and error, then they might boil it even if it looks clean, but they'd be more likely to find another source if possible.

Lastly, rain water can be gathered rather easily, and it was definitely used for drinking, as we know from many castles having huge cisterns to store it. Aside from cities and castles, it probably wouldn't be all that popular, since villages tended to have wells or streams nearby, but it could be used occassionally.

2) Non-alcoholic drinks

Making hooch isn't the only way to get safe drinks. Some drinks, like coffee or tea are made safer just because they have to be boiled, and these were, in a way, known in the medieval times too. You obviously had little tea preior to colonial empires, but oral tradition does come to the rescue. Local herbs were used not only as remedies, but sometimes to just have a good tasting drink that will warm you up. What was used depended on what was available, but most common variant were strawberry leaves, whether fresh or dried.

Let's also not forget what we would call juice, made of either fruit or vegetables. Apple ciders were especially popular, and apples were often stored over the winter (you can do so without drying them, if you know how), so they were available all year round.

Last but not least, we have milk, and that was a huge, huge source of drinks. Almost every single family had at least a cow or two, not counting sheep, goats and so on. There were recipes to prepare milk in all the ways imaginable, from sweetening it with honey (it's delicious, by the by) up to and including making into hooch.

3) Alcohol

This is the one people talk most about - ABV content was rarely over 30% during the middle ages, though. You need to distill stuff to make drink that strong, and that process wasn't invented quite yet, or at least not widely known. You can get strong concentrations of alcohol, around the 30% mark, byy freezing the drink and taking out the ice, but stuff like this was expensive.

Making the drink less potent by adding water was also popular, as was sneakily putting in water to rake in profits, as we know from many, many laws that detailed penalties to innkeepers who did it.

4) What DID they drink, then?

Well, this depends on the person in question. It's quite likely that a rich dude rarely drank pure water, having alcohol, honeyed milk or some other thing nearby. Traveling people usually used what was nearby, and usually tried to avoid local water, it seems - inns had tidy profits from selling alcohol to them.

People who couldn't afford to stay at an inn, well, that's something we know pretty much nothing about. If they had a cow with them, milk seems like a ready made source of fluids, otherwise, wells and springs would be preferred, and in a pinch, a stream will do. Using local herbs to make "tea" is also possible, especially is they weren't in a hurry.

Locals would drink water in reasonable quantities, if only because they were well aware which source is clean and which isn't.

Soldiers, well, all of the above, it really depends on what situation they're in. Sometimes, situation was desperate enough to just straight up start drinking from whatever was available, and as you can imagine, that rarely ended well - dysentery is what you get if you're lucky.