A few years ago at ATH everyone was forbidden to bring empty water bottles through security. I don't know if they are still doing that.

And a couple years ago at VIE, I found that after going through gate security with an empty water bottle, there were no water fountains at the gate to fill it in. There was a rest room at the gate with sink faucets, but I was dubious about that since in some countries such faucets aren't always drinking water, and even if it is, drinking it seems kind of gross -- who knows whose hands have been on those faucets?

(And no I don't feel the same about drinking fountains -- what goes on in the immediate area of a public drinking fountain aren't the same sort of things that go on in a toilet.)