yukonjasper wrote:When its cold out, they make insulated camelbacks that I've used for skiing and winter camping. I have worn it under my coat so my body heat keeps it from freezing and if you do it correctly and put warm water into, it can keep you warm while you wear it and when you drink it because your ingesting a closer to body temperature liquid
And while I didn't dig mine out to check, I'm pretty sure the tube is insulated right up to the bite valve. Also, when you're done sipping, blow the liquid back into the bladder to keep it at the preferred temp- be that warm or cold.