Not true everywhere, actually never heard of it here (Germany and Austria).

But if you walk into a place and ask for a paper cup of tap water, a lot of workers are willing to give it to you, regardless of the laws.

Vienna has tap water straight from the mountains btw and it tastes amazing. Recommended.

Here in the US, this seems so normal that it didnt even occur to me that this may not be true everywhere else. And not need to be enforced by law.

Then there's Germany where restaurants charge you 6€ for a jug of tap water.

Yep, can confirm for Portugal.