The self-cooling beer can exists! Check this out:
http://www.realbeer.com/news/articles/news-002203.php
Self-chilling beer can
British can expect to see cans that cool with a twist by summer
Apr 29, 2004 - A self-cooling beer can that chills beer to only a few degrees above freezing is headed for British retail shelves this summer.
Selling cold beer to the Brits? That's a sure-fire flop.