Because dogs have four legs on the ground, the arrangement of the digestive tract is parallel to the ground, while because humans have two legs on the ground, the digestive tract is vertical to the ground.
Because there is gravity, people are not very good at vomiting; because dogs lack this gravity, and their stomach is very close to the rectum, they can easily vomit before defecation, when they are constipated, or when their food is a little wrong.
Sometimes vomiting is a self-healing process, because vomiting makes them more comfortable. But if it has a disease, vomiting, and other symptoms, you have to see a doctor.
Some puppies secrete stomach acid due to hunger in the morning, and nausea will spit out some acidic water.
At this time, the eating time must be adjusted immediately to avoid long-term corrosion of the stomach and esophagus and causing upper digestive tract problems.
Puppies are more likely to feel nausea or vomiting, which is often the reason for their loss of appetite or picky eating.