Water streaming through holes in the bottom of a suspended soda pop can causes the can to rotate.
Lay the pop can on its side and using the nail or ice pick carefully punch four equally spaced small holes just above and around the bottom rim. Bend the can's opener lever straight up and tie a short length of fishing line to it. Immerse the can in water until it is filled. Pull the can out by the fishing line. Water streams will start the can spinning.