Welcome to HCM,
Your father is diabetic and recently recovered from Urinary tract Infection
,as he was hospitalized, I presume antibiotics were given through injection,but if he is taking insulin he needs to eat and if he is vomiting there may be some cause for it like if there are any drugs which have caused drug induced Gastritis
If he is not tolerating orally please contact treating physician to give treatment for it like Antacids,PPI like Omeprazole
and if required anti emetic like Domperidone
may be required.
Other thing is if his blood sugar is high and there are some renal of liver issues.
Please take very good care of him