He is throwing up. There are at last 5 different ways to say what he is doing. "throwing up" was the first one in my mind, and the one I learned first as a child because that is what moms use when talking to children in America in the 1960s.

Vomit

Vomit мне кажется?

to vomit, to throw up, to puke (informal)

Throwing up, being sick or vomiting