Since we are going off on a tangent, a cool camping hack when you don't have ice is to stuff a beer in a tube sock, dunk it in water, and hang/tie it to a tree branch in the shade. If there is even a touch of wind it will be nice and cold in 10 minutes.
Evaporative beer cooling.. very clever. I wonder if there is a market for a product dedicated/optimized for this (incorporated drawstring/hanger, ideal material, etc.)
"Billy Mays here for Beer Sock!"
This is much more elegant than the spinning trick, as it doesn't require energy input.
Works really well in deserts, if you keep the sock in the shade.
I wonder if you wound up the sock and let it spin if you'd get something virtually equivalent to this machine.