I always bring my own little bottles when I go on vacation. Sometimes, I have been allowed to use it on the plane, other times, not. Never been a big deal and my 99 cent bottle is a lot less expensive than theirs. If I can’t drink it on the plane, I have my drinks where ever I stay.
Oh, and there have been times, I buy a coke at the fast food place before boarding. I am always allowed to take that on board(and it is spiked). I drink at the airport. It is my thing, I guess, cuz I don’t care for flying.