There is a water fountain by the toilets near a2 and again by the toilets after b2 in terminal one. You can’t take liquids with you through security, which happens at the gates.
Recently flew out of b2 though and there’s another fountain right by the toilets inside the seated area after security.
Not sure if this happens at every gate, but definitely an improvement on previous progress vision and generally a nice touch.
#plasticfree @PragueAirport