I have a 1 quart bottle that has a built in straw, and seals well enough to not leak (important, since I'm in and out of the car frequently during the day). I drink tap water here (some houses we've lived in, I've gotten filtered water, but here the taste is OK), always over ice. I can tolerate room temp, but much prefer very, very cold. I fill it in the morning, carry it with me, and just sip on it and re-fill it when it's empty. I always have it with me at meetings, as I find I drink a lot then. I think I drink a gallon or more most days, but have an occassional day where I have trouble getting that much -- usually when one of my kids has absconded with my bottle!