While Diet Coke and Mentos are the most common way to make a soda geyser, they are not the only options.  Many consider Diet Coke to be the optimal option. While Diet Coke has been studied and suggested that it has the strongest effect, at least one other study has demonstrated that all diet sodas essentially work equally well within experimental error. Nevertheless, any carbonated beverage will work.  As for the Mentos, many things work to nucleate carbonated beverages such as other candy, metal and ceramic spheres, and even sand.