every iteration of foldable waterbottles (vapur, camleback, nalgene) i've owned has leaked very early in its life. Dromlite and gatorade. I'm a fan of the 2 liter rectangle shaped opaque plastic nalgene if I use flavored water. I only care about funky taste cragging. Alpine i'm too thirsty to notice. Like cheap sunglasses, because the gatorade bottles are so cheap, you will never lose them.
Blake is on the money with adding gatorade type powder. Also don't fill it all the way. The sloshing will help it from freezing.