That really depends on the country. In Denmark you wouldn't expect to have to pay, although a few places charge people. Often this is done more as an anti-homeless thing than as a revenue generation thing.

In Germany you should expect to pay for a public toilet visit. Enforcement varies, from just a dish of coins with a sign urging you to "tip" the cleaning staff, over a grumpy looking lady sitting next to the dish, shaming you with her eyes to leave a "tip", over said lady only handing you the key to the restroom after you've paid her to having actual turnstiles preventing freeloaders from relieving themselves. As far as I understand this tipping culture exists as a result of the cleaning staff being paid dogshit wages so you should absolutely leave a tip if you're able to.

I can't remember how it is in Sweden but I don't remember it as being as pervasive as in Germany.