Hi,
Abdominal pain, vomiting, and diarrhea can be symptoms of several different conditions, including viral or bacterial infections, food 
poisoning, 
inflammatory bowel disease, and other gastrointestinal disorders. In your husband's case, it is possible that the donut he ate was contaminated with harmful bacteria or viruses, which can cause food poisoning.
Other possible causes of these symptoms include:
* Gastroenteritis: This is an infection of the stomach and intestines caused by a virus, bacteria, or parasite. Abdominal pain, diarrhea, vomiting, and fever are some of the symptoms.
* 
Irritable bowel syndrome (IBS): This is a chronic condition that affects the large intestine. This condition can lead to abdominal pain, diarrhea, and/or 
constipation.
* Crohn's disease or ulcerative colitis: These are two types of inflammatory bowel disease that can cause abdominal pain, diarrhea, and other symptoms.
* 
Gallbladder disease: This can cause abdominal pain, nausea, and vomiting, especially after eating fatty foods.
It is important to seek medical attention if your husband's symptoms persist or worsen, or if he experiences severe abdominal pain, 
dehydration, or other serious symptoms. Treatment will depend on the underlying cause of his symptoms and may include antibiotics, anti-inflammatory medications, or other therapies. In the meantime, he should drink plenty of fluids to stay hydrated and rest as much as possible.
Take care. Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. Priyanka, General & Family Physician