Cucumbers make you burp due to a chemical called cucurbitacin which is located at the stem end of the cucumber.
The chemical "cucurbitacin" that cucumbers contain is what causes people to burp and cause gas buildup in peoples stomachs and possible stomach pain.
The chemical "cucurbitacin" is also a cause of bitterness in some cucumbers.
The cucurbitacin can also sometimes cause indigestion in some people so it's best to avoid eating too many cucumbers if you suffer from digestive issues.
Although cucumbers are very healthy for you but sometimes you might not be able to eat as many as you'd like if they're causing stomach problems.