My 3 year old brother isnt running a fever anymore but he is still throwing up?

what do i do? he had a flu and he was sick with a fever for like 3 or 4 days, but the fever is gone but he is still throwing up. my gramma and grampa are at work right now so i have to take care of him ((im his sister, im 14)) so how do i get him to stop throwing up?