Mythbusters did an episode on the mentos in diet coke. With a small nozzle, they got it to shoot over their 3 story building. I still haven't tried it myself.
My parents are doomed. The next time I visit I am setting this up. In the past I have always left a rubber band around the trigger on the spray nozzle by the sink. They have come to expect it. They'll never see this coming:rofl: