Explanation: Ever have one of those days when you have to eat lunch out of a vending machine? Anyone whose heard the Internet-fueled rumor about the guy who ruptured his stomach by downing Diet Coke and Mentos will probably avoid that sugary combination on such occasions. Yet, as with many cyber sensations, there's a lot of hot air behind the Diet Coke and Mentos rumor.
It's true that if you drop a pack of the chewy mints into a 2-liter bottle of Diet Coke, the candy's properties react with the carbon dioxide in the soda to spew forth fizz. Physicist Tonya Coffey determined that this happens because Mentos' rough surface breaks up the attraction between water molecules in the Coke, clearing room for carbon dioxide bubbles to form. The gum arabic further fuels the fizz by making the candy fall through the liquid faster, which causes bubbles to form more rapidly.
However, when you open and drink a Diet Coke, it releases much of the pressurized carbon dioxide that forms the carbonation. As the soda warms while traveling to the stomach, the gas continues to vaporize. Any remaining might cause your stomach to expand, but it isn't enough to spark a dangerous gassy rebellion if you chase the soda with a pack of Mentos.
The nutritional value of a Diet Coke and Mentos snack is still questionable, but if that's your only vending machine vice, your stomach should make it through just fine.