I don't know about the rest of Europe, but in Germany bars have to provide free tap water if you ask for it. They also have to offer at least one non-alcoholic drink that's cheaper than the cheapest alcoholic drink, IIRC.
That's a myth, they can charge whatever they want for it.
> They also have to offer at least one non-alcoholic drink that's cheaper than the cheapest alcoholic drink
That is actually true.
http://www.swr.de/marktcheck/restaurant-irrtuemer-top3/-/id=...