Fill a standard Nalgene bottle or USGI canteen with hot water, and place it inside the sleeping bag near the feet. A quick and easy tip that I've been using for years, and it never fails to keep me warm until I fall asleep.<br><br>Also, I agree with aardwolfe, a "pee bottle" is a great idea, and something I also use. Just make sure the cap is a noticably different color than the ones your are drinking out of. <br><br>John McIntire