Soda + Mentos = Explosion, QUESTION!!!?

I am going to do a science project on soda and mentos... I know how and why it makes an eruption when you drop the mentos into the soda, but why do some certain sodas work better than others? I am going to test Diet Coca-Cola, Regular Coke, Root Beer, and Sprite... Could someone tell me why one of these sodas will have bigger eruptions than the others??? Like do they have certain ingredients??? And what are those ingredients, Please help i need the info for my science project :)