Self-serve soda machines are a convenient way to help yourself to a thirst-quenching drink, but they might not be the safest way to get a beverage. It turns out the machines can make you sick, and a former health inspector has shared how to tell if you should avoid using one.

They posted their warning on Reddit, writing, "If there's a self-serve soda machine go ahead and take a napkin around the inside of the Sprite/clear-soda-available nozzle. If your napkin comes out pink, brown, or orange skip the soda. A Sprite nozzle should come out clear. If it's pink or orange then it's slime mold (it's actually a bacteria, but that's what we called it). If it's brown, it's likely cola. But if the Cola nozzle was put on the Sprite dispenser and is still brown, you know the nozzles aren't being cleaned properly." They also suggested looking at the soda machine's ice chute for green algae.

It's sound advice since in 2010, a study showed that nearly half the soda fountain beverages tested had coliform in them, a bacteria that indicates a possible fecal contamination. Further samples had other bacteria that can make you sick, like E. coli.

The good news is, most major fast food restaurants take good care of their machines, with commenters saying things like, "I worked at McDonald's for a few years. We were required to pull the nozzles every night for cleaning," and, "Burger King had the most extensive cleaning schedule I've ever seen in a fast-food place, at least where I worked."

Nonetheless, if you are at a restaurant that has a self-serve soda fountain machine, it's always best to be safe and take a moment to check the nozzles before you use them. Meanwhile, the machines might become a thing of the past. Some places are getting rid of them, like McDonald's, which recently announced plans to eliminate all of the self-service fountains from their restaurants by 2032, citing how consumer behavior has changed since the pandemic.