COKE + MENTOS

When the candies come into contact with the liquid, a reaction causes the formation of foam at a rapid rate.

Diet Coke + Mentos = formation of foam
Potassium benzoate, aspartame, and CO₂ gas + gelatin and gum arabic = formation of foam

  

The structure of the Mentos is the most significant cause of the eruption due to nucleation. When fruit-flavored Mentos with a smooth waxy coating were tested in carbonated drink there was hardly a reaction, whereas mint-flavored Mentos added to carbonated drink formed an energetic eruption, affirming the nucleation-site theory.

 The surface of the mint Mentos is covered with many small holes that increase the surface area available for reaction (and thus the quantity of reagents exposed to each other at any given time).This hypothesis gained further support when rock salt was used as a "jump start" to the reaction.