Dogs vomiting gastric juice are usually caused by eating too fast, eating too much, improper diet, indigestion, gastrointestinal diseases, or viral infection. If the dog only vomits once, it will be fine. Just need to Just fast for the dog for a day and then feed some probiotics to regulate the stomach. If the dog vomits for several days in a row and is accompanied by diarrhea, lack of energy, blood in the stool, etc., it is best to send it to a pet hospital immediately for examination and treatment.