When a human vomits, only about a third of the stomach contents is reliably returned.
There are some frog species which can vomit much more efficiently. If you have a strong stomach, you can see the evidence and the mechanism by clicking HERE.
The stomach is everted (turned inside out) in full view of the observer, and wiped clean by the frog, before re-swallowing it. This extra effort serves as protection for the frog after eating such things as poisonous insects.
Fortunately the stomach contents aren’t too disgusting in appearance, so go ahead… you can watch it…..