Carry an empty water bottle to the airport.

Photo by Kristopher Patterson on Unsplash

Most major airports have water fountains where you can refill your bottles once you've passed security.
This way you don't have to pay ridiculous prices for water.
I like to carry a foldable one with so it doesn't take up much space in your carry on.

You can even refill at hotels and restaurants as you go - you don't have to be a guest at the hotel and most won't charge you for this service.

Promising Review : CalamityJ

So convenient for traveling. Well made, sturdy, a great product.