I am guessing you just got fed up with your Ex girlfriend or boyfriend but to drain your battery simply leave the car light on for about 24 hours. Make sure that the car is not running and nobody drives it during the time the lights are on. Hopefully you have good intentions with a drained battery but if you change your mind you can charge your battery by going to a shop or simply driving really fast. In addition there are machines that can jump start a drained battery.