No their can be as little as one mento. Each mento, hard or chewy, has lots of bumps on it, it makes it look like the surface of the moon, each bump (one of millions) lets of air bubbles at an alarming rate and they don't stop entirely until they ether get taken out or dissolve. It sink to the bottom so that the bubbles have time to form together and then that's what causes it to explode... Yet I still want to know why they use 'diet' coke?
When you put "Mentos" into the diet "Coke", there will be an eruption of "Coke". Sort of like a volcanic eruption. But there has to be about eight Mento's dropped into the Coke simlutaneously.