When I travel, I bring an empty cycling water bottle with me and send it through the x-ray with the top off so it's obviously empty. Once through security, I fill it up in a water fountain and hydrate for free.
Yes, I do this too. Incredibly, a lot of airports only have hot water in the bathrooms. Or sinks designed in such a way that a bottle can hardly be filled at all.
Only place I've seen that had an actual bottle-fill station was Copenhagen airport in Denmark. But in many ways that airport felt like it was 10 years ahead.
Pretty sure I've seen them in Salt Lake & Heathrow
...and Portland, OR and Orlando, FL.
They're growing in popularity.
Pittsburgh, Chicago, Dallas Love Field and Dallas DFW all have special places in the water fountains for large water bottles. Of course it is generally cold as it is in the US and we like our beverages below room temperature ;)