some throw up because they ate something they shouldn't
sometimes drinking way to much water
playing too hard
eating to fast also causes vomiting
but its always good to tell your vet
you didn't say how often he vomits?
I have a 10 week old puppy,she threw up kibble and what i know was carpet she chewed on,she was fine after and ate her reg meal
Make sure you dog doesn't have the runs
and as long as he is healthy otherwise,you needs to watch him and see if its drnking to much water,eating to fast,or this happens when he plays to hard