What is the baking soda and vinegar challenge?

The "baking soda and vinegar challenge" is a game that has become a viral meme on the Internet. Participants combine the two substances in their mouths and try to hold the resulting foamy liquid in for as long as possible.

When combined, baking soda and vinegar create carbon dioxide gas, causing the liquid to fizz violently. This and the unpleasant taste are the key components of the challenge. People commonly film themselves taking the challenge, and they post it on YouTube. It is most commonly done by children and teenagers, though some adults have also posted online videos of themselves taking the challenge.