Why does Diet Coke and Mentos React?

Diet Coke and Mentos react in an ‘explosion’ because the candies cause the soda to foam at a very rapid rate, and then it has no where to go but up and out of the bottle. The force causes it to stream upward. You can use regular soda, but people have found diet to work best. It is a great science experiment, because it is safe, cheap, and effective.