What happen when you add Mentos to coffee?

Here's why:

* No Carbonation: Coffee, unlike soda, doesn't have significant carbonation. The Mentos won't have anything to react with to cause a fizz.

* Different Ingredients: The reaction with Diet Coke is based on the interaction of Mentos's rough surface with the dissolved carbon dioxide in the soda, creating a rapid release of gas. Coffee doesn't have this.

* Taste: Adding Mentos to coffee will mostly just make your coffee taste like Mentos. It's not recommended for a pleasant coffee experience.

However, you might notice:

* Slight fizz: Depending on how fresh the coffee is, you might see some very minor bubbles forming, but it won't be anything like the Diet Coke fountain.

* Change in Flavor: The mint flavor of the Mentos will definitely mix with your coffee, creating a less-than-desirable flavor profile.

In short: You're better off sticking to sugar or cream for your coffee, and leave the Mentos for your soda.