I have a Daschund who is 3 yrs old. He has had vomiting issues before and Vet said it was sour stomach when he does not eat, but in the last week he has woke up very early vomiting, yellowish stuff . I leave him outside and he is out for a few minutes. Then OK. It seems if he eats later in the night he is OK early AM. Is this something I should be concerned about or sour stomach? If so what can I do to help him ?
Thanks in advance!

My dog has the same problem from time to time. She was just to the vets recently and I mentioned it. The vet didn't seem concerned at all. She said that it was bile.