Mixing Coke and Mentos causes a fast, foamy eruption — basically a soda geyser.

Here’s what’s happening: Coke is full of dissolved carbon dioxide gas. Mentos candies have lots of tiny pits on their surface, which give the gas places to rapidly form bubbles. When you drop Mentos into the Coke, the carbon dioxide rushes out all at once and pushes soda upward in a big fountain.

A few practical notes:

• Diet Coke usually erupts higher than regular Coke because of its ingredients and lower stickiness.
• The reaction is physical, not chemical — you’re not creating a dangerous new substance.
• It’s messy, sticky, and pressurized, so do it outside, away from people, pets, cars, and anything electronic.
• Don’t screw a cap on after adding Mentos — pressure can build up and make the bottle burst.
• Never put Mentos and Coke in your mouth together as a prank; it can cause choking or sudden foaming.

For a classic experiment: use a 2-liter bottle, drop in 5–7 Mentos quickly, then step back immediately.

👉 Are you trying to do this as a science experiment, a prank, or just curious what would happen?