Get a big bowl of ice, cover the beer almost entirely, then spin that little sucker in the ice til it's cooler than cold

The quickest method is to submerge it in ice-water mixed with salt in a cooler. Saltwater remains liquid at colder temperatures, is why. Per this test, it took about 3.5 minutes for a 12 ounce can to get to drinkably cold from room temp.

You can try this if you like MacGyver: http://www.instructables.com/id/Ice-Cold-Beer-In-20-Seconds/