I really like the Brita water bottles with the filter built into the mouthpiece. You can pack them empty in your backpack or messenger bag or whatever it is you use for your carry-on, and once you're through security, you can fill them at the tap or the drinking fountain and not have to pay for water. And then for the rest of your trip if you're somewhere with great water, no harm, and if you're somewhere the water is kind of foul-tasting, it will be improved before it ever reaches your lips.
They're very light, they're not very expensive--far more cost-effective than buying drinks on the far side of airport security--and they come in nice colors. There is a little loop you can use to clip them onto your bag if you have a carabiner. I bet lots of you have carabiners. Everything but the little filter bit can go in your dishwasher when you get home if you have a dishwasher at home. It is muchly convenient.
This is your deep, analytical post for the moment. We had lots of good conversation about books and stories and art and genre and like that, and about other things too, and maybe I will even find things that I can say about them instead of making the face of thinkiness over here. But in the meantime: Brita water bottle. Ayeh.