If you are going to give a child with vomiting and diarrhea soda, it is a good idea to make sure that it has gone flat, otherwise the carbonation will likely make your child's stomach feel even worse. Soda, whether it is Coke or 7 UP, is not a good fluid to give a child with vomiting and diarrhea though. An oral rehydration solution, like Enfalyte, Pedialyte, LiquiLyte, or Rehydralyte, are much better options, as they have the right mix of sugar and electrolytes to prevent and treat dehydration.