Water did not do anything.
The Seltzer Water acted like my volcano
But, the sodas did alot of things, they all just exploded. The Diet Coke exploded big. The Caffeine Free one exploded a little higher than the seltzer water, but lower then the Diet Coke.
We need caffeine to make the big explosion.
We tried it with Fruit-flavored Mentos, and regular Diet Coke. We had fun with that.
The Mythbusters used different ingredients plus mentos to find out which ones worked to go 30 feet high. They had a cool thing with that, and it was fun to see that.
Here is a video of me dropping mentos into a bottle of Diet Coke.