Sometimes I burp after eating food in Minecraft (Java edition 1.13.2 on Linux in a singleplayer world). First, the food will be consumed as normal, restoring the expected amount of hunger. Then I hear a "burp" sound and additional hunger is restored. Since this usually happens unexpectedly, I don't know whether additional food has been consumed or not. What causes the burp? What are its effects? And can it be done intentionally?
The second food consumption is caused by the bug MC-849. Under certain circumstances, it's possible to accidentally eat a second food item, without seeing it, slowing down your movement or a chewing sound.
The burping sound still plays, since it's caused by the server telling the client that eating is finished. It also plays after the first food item, but it's hard to hear due to the eating sound.
From the list of sound effects the sound is purely random.
The extra food can sometimes be attributed to latency when consuming food, and may sometimes try to "catch up", leading to consuming extra items of food.
It happens, when you eat some food that fills your hunger bar entirely. The hunger bar you see on screen is just 1/2 of the bar. Actually your maximum hunger level is 20.
When it reaches 20, then the burp sound plays but not every time.