Teddy can eat grapefruit, but it is not advisable to eat too much. Occasionally feeding grapefruit can effectively enhance the dog’s gastrointestinal motility because it is rich in fiber and water. However, overfeeding it will have the opposite effect and cause the dog’s gastrointestinal motility to increase. Dog diarrhea. Moreover, grapefruit is a cooling fruit and contains more sugar. Long-term feeding can easily induce gastrointestinal and dental diseases in dogs.