Burping is a natural process that occurs when the body tries to clear excess gas from the upper digestive tract. On Earth, gravity helps separate the gassy ingredients of a burp from the liquid and solid remnants of food in the stomach, allowing gas to rise into the lower part of the esophagus and escape as a burp.
However, in space where there is no gravity, the process is much more complex. Experts say that astronauts can’t burp in space like they do on Earth because gravity helps sort out the contents of their stomachs. Without gravity, the air and liquids in the stomach are mixed up, making it difficult to separate the gas from the liquid.
Astronauts may experience reflux instead, where stomach acid and partially digested food can come back into the esophagus, causing discomfort. However, if an astronaut wants to burp, they can create their own artificial gravity by giving themselves a good shove away from a nearby wall. This temporary acceleration helps sort out the stomach contents, allowing gas to rise into the esophagus and escape as a burp.
The mechanics of burping depend on gravity, so without it, the process is messy. While astronauts don’t have to worry about badly timed belches, they do face challenges related to reflux and farts in space.
Source: https://www.livescience.com/space/space-exploration/can-you-burp-in-space