I'm late in coming to this but will reply from my experience. Sugar in the gas tank does indeed work and does damage the engine. The pistons seize up and stop moving. The car has to run a short while before it takes effect. The ping pong ball idea is also a good one and uses the same principle as something I know about. Pour a jar of pickles into the gas tank. Make it sweet pickles and you get a double whammy. Of course, not everyone carries sugar, ping pong balls or pickles around with them, so it has to be planned rather than a spur of the moment thing. If it's on impurlse, you can jam the valve on one or more tires with a toothpick or matchstick. It goes a little way before all the air escapes. Slashing the sidewalls is very effective, but immediate.
My knowledge is gleaned from having once taught some very mischievous
