Hello and thank you for your question.
Hold old is your child? Is he otherwise healthy and doing well?
It sounds like he may have picked up gastroenteritis, causing loose stools and vomiting. In terms of feeding after vomiting, it may depend on the age. Infants (less than 1 year) can be placed back on formula, but use small amounts at a time. Half an once or less. I do not recommend watering down the formula or letting him drink water however. You could also give him some pedialyte, again in small amounts.
For the older kids, I usually advise people to keep the diet bland and the amount relatively small. You could start with crackers or toast for example, but go slowly. If they seem to tolerate that well without further vomiting, you can advance the amount and the type of foods given.
It's also important to make sure kids with vomiting and dirrhea are not becoming dehydrated. As long as he is urinating, he probably doing ok, but if he were to go more than 8 hours without a wet diaper, I would be more concerned and seek medical evaluation.
Please let me know if this answer helps or if you have any further questions.
In that case I would feed him his usual diet, but start off slow. Allow him to drink, but avoid too much juice or anything with any caffine in it. Again pedialyte is a good oral rehydration solution in this age group.
Gastroenteritis may also be known as a 'tummy bug' or 'stomach flu.' It is vomiting and diarrhea together, often with fevers and generally just not feeling well. Gastro is genearlly caused by a virus, meaning that there aren't any antibiotics which will help him get better faster. Most cases last anywhere from a day to five or six days, depending on the cause, and there are many different types of viruses which can cause gastro. We don't generally test to find out which one it is.
If he's not getting better in the next few days or if you see bloody stools, then he should be evaluated for other causes of his diarrhea, which could include various types of bacteria. You physician would be able to send his stool for cultures and see what grows, but in general, this is not necessary. Certain foods do put you at risk for contracting bacterial gastro, including undercooked hamburgers or undercooked chicken. Again, in an otherwise healthy child, who is making regular urine, the most likely cause is still a virus.