Depending upon whats wrong with it there are different things you can do. If your nauseated them you can take something like pepto bis-mouth and eat soup and soda crackers. Drink plenty of water and you can dri coke or sprite to help with the nausea. If you have diarrhea then you can take something like Imodium ad or pepto bis-mouth. That is good for most stomach sysptems.and again drink plenty of water and for direah you want electrolytes back in your system so drink something like powerade or Gatorade