Unchilled Tab-Water and filling bottles in the bathroom. Some drinking fountains are publicly available but more of a novelty and none usually not inside of buildings.

I don't know about others, but getting hydrated isn't an issue here. It's rarely significant above 30°C even in summer (and if max 2 months) and our water in my city is of such "high quality" they bottle and sell it. (Aqua di Monaco).