for 1.. diet soda gives a better reaction... and second of all... drinkin alot of pop and then eating a bunch of mentos wont do ANYTHING but give u the burps..... its not huge mysterious scientific answer to why it does that... bottom line.. what the shell of the mentos is made out of.. breaks the surface tension of the soda much faster then anything else does... and as u know.. when u break the surface tension of anything carbonated at a fast rate.. u get a violant eruption..... this experiment works not only with mentos.. but also with other candys similar to mentos.... such as shock tarts.... and.. u can even use Tonic water or any other carbonated beverage...