Dogs cannot eat tomatoes, onions, and mushrooms. If they eat them, they will easily suffer from vomiting, diarrhea, and even dehydration, shock, and death. So do not give these three vegetables to your dog casually. . Dogs can eat vegetables such as carrots, potatoes, broccoli, and cabbage, but do not feed them too much at one time to avoid gastrointestinal discomfort and indigestion.