Pack An Empty Water Bottle
Want to save money at the airport? Pack an empty water bottle. In most cases, you would have to throw away a bottle with contents in it, so to avoid that and spending a ridiculous amount on a bottle from the airport, just bring an empty bottle.
Airports have water fountains where you can fill your empty one right up. Think of the money it will save you not buying water on the plane as well. It will save your flight attendants time, too. Why bother them with getting you a water bottle when you could have pre-filled one yourself.