It could be food, a body cold, or it might be time to deworm.
When a dog vomits, there are generally two situations:
1. It might be common gastroenteritis. Generally, gastrointestinal discomfort can cause vomiting, or eating dirty food can also lead to gastrointestinal inflammation and vomiting. You can give it some medications to treat gastroenteritis, such as fluoroquinolone, gentamicin injection which can also be administered orally, and additionally some human medicines like metoclopramide tablets, which is very easy.
2. It might be parvoviral enteritis or canine distemper. You should see if there are other accompanying symptoms, such as fever, eye discharge, coughing, shivering, etc. If there are, then testing should be performed. You can go to the pet hospital for testing or buy test strips yourself to test it.
If it is indeed one of these two, it should be taken very seriously: immediately inject the dog with refined canine pentavalent serum, combined with antibiotic treatment. Antibiotics can include penicillin, streptomycin, florfenicol, cephalosporins, etc. If that doesn't work, infusion therapy should be done, along with plasma, monoclonal antibodies, etc.