What Is The Best Thing To Give A Child For Vomiting?

My 14 year old, non-verbal Autistic son started the week with severe allergies. As of Thursday, he has a chronic cough and has been vomiting. The vomiting was the worst today. Any OTC meds I give him, either don t work or cause more vomiting including his Prevacid. There is a low grade fever that comes and goes. I would not be concerned if he was able to rest this evening, but he coughs himself awake. I gave him a 325mg acetaminophen suppository to help with any pain of headache or body aches. I cannot seem to find the right medication or solution. I don t think this is viral, but I don t really know now. What should I be looking for? It has been more than 48 hours.