Not all European countries have tap water that’s safe to drink. In Germany you can get away with that, in Spain I wouldn’t risk it.
In most of Spain the tap water is totally safe to drink. I would avoid it in the islands only.
Toilets aren't exactly a good source to refill your water bottle for obvious reasons.
Use the sink instead of the toilet.
I was referring to the bathroom sink. Potential cross-contamination is much higher there than from any other usual tap source, especially in a public bathroom.