My daughter has been dealing with that since she was about 6 years old. She randomly wakes
up sick in the morning throws
up a few times
and then is fine. We spent a lot of time trying to figure out if it was a certain food item, but it's not. We try to control the symptoms by taking Zantac 75 before dinner (per doctor recommendation), and not eating for several hours before bedtime, this has helped quite a bit, although she still gets flair ups from time to time.