Don't just drink your milk... have fun with it! Check out this science experiment video to see how to curdle milk with a battery and salt. This experiment can be done by anyone with a few simple materials... milk, a 9-volt battery, a small glass or plastic cup, salt and a stirring rod.
Pour the milk into the cup of salt and stir with the stirring rod. Now, take the battery and dip the connectors into the milk and watch what happens -- curdled milk. Now, you're battery maybe useless after this electricity study, but who cares... it's just a battery.