If your child has a " virus "..........there is no cure. Just make sure your child has SOMETHING in the stomach, to bring up. Toast, crackers, pieces of fruits, bites of cheese...........there is no need to let your child go into the " dry heave" scenerio.
Personally, I tend to think that the medical field calls it a " virus", when they can not identify what they are dealing with..........
Do give plenty of fluids to your child, but not milk, which can indeed turn sour in the stomach.
Water, juices ( not overly sweet) and Pedilite are all recommended, as well as chicken broth.
If the situation does not improve after 24 hours.......seek medical care, if you are truly worried, don't wait that long.