My five year old has vomited for 3 days, but goes hours (approx 6-8) between vomiting, has no fever and has felt normal otherwise. what could it be?

Possibilities: This could easily be a simple virus or a reaction to an ingested food or drink. Since foods take a few days to be fully processed they can trigger a reaction until the process is completed. Either will pass over time.As long as the kid stay hydrated & able to feed around the episodes it should remain mild. Consider any new food exposure for exclusion if that is a consideration.