What Could Be Causing My Autistic Toddler To Vomit After Drinking Pediasure And After Car Rides?

My sin is use to drinking pediasure no issues ever, but last night he threw up 3 times. Twice pediasure and the last was regular food. He went all day today with no throwing up until about 6 pm and so far has only thrown up once. He doesn t really want to eat anything either. He will be 3 in February and he is also autistic so it s hard to get him to eat a good that s why I give hum pediasure. He also has no fever. He threw up the first time after a car ride once we got home and the threw up 2 more times after that. Then tonight he threw up the first time after a car ride again.