Thank you for your query,
Your child is having Gastroenteritis
which may be viral or some times bacterial.
For vomitings you can give anti emetic like ondansetron or domperidone
in prescribed dosage to decrease vomitings.
Give sips of oral rehydrating solutions to prevent dehydration
Consult your Pediatrician
for the assessment of hydration status and for specific treatment.
Hope i have answered your query.