Glad to know I'm not weird for leaving an open bottle of water out on the counter all the time (there are so many other reasons to be weird). My teeth are cold sensitive too, plus even though the water here is pretty good, letting it sit for a while makes it sweeter and less metallic tasting. If (if - hah!) I get up in the middle of the night, I walk into the kitchen and swig some (helps prevent morning mouth), also drink at least eight ounces as soon as I get up in the morning. This way, I drink a liter by 9:00 a.m. and it's easy to drink at least three a day, all I have to do is make sure I refill and empty it twice before bed.