The ping-pong-ball-in-the-gas-tank trick won't work on most cars (at least, in the US). A ping-pong ball is 40mm in diameter (roughly 1 9/16"). Since the mid-1970s, all gasoline-powered vehicles sold in the US have been required to use unleaded fuel. The filler spout on an unleaded pump is only 13/16" in diameter and cars' filler tubes are built so that it's impossible to get anything larger than that into the gas tank. You could do it on an older car or a diesel-powered vehicle, but not the vast majority of modern cars.