5 year old Grandson has been waking up to vomit past several nights. After vomiting seems fine. Also seems fine during the day. Begins to complain of stomach ache at night. Also complained of stomach ache and not feeling well after eating meal of pasta and then getting in warm jacuzzi. He's not a very good eater in general and prefers high carb and sugary foods & drinks as most kids do. He is tall and thin for his age. My daughter took him to the Dr and they believe it's a stomach virus. No fever or diarrhea, stools are firm but no constipation. Daughter says his vomit has a sweet-sour smell and sometimes he burps, and burps will smell like his vomit. Is is possible he's suffering from some form of low blood sugar? Just seems strange that symptoms occur mostly at night.