What is the best thing to drink after throwing up?

Water or Gatorade: Vomiting can cause dehydration. Especially if you are sick for several days and vomiting a lot, make sure you are drinking a lot of fluid with electrolytes (gatorade, powerade, etc). Always make sure you are getting plenty of water as well; after vomiting drinking small sips of water or an electrolyte rich drink might keep you from vomiting again.

Why throw up: It depends on the reason of why did you throw up. If it was due to a infection of sort or something that made your stomach irritated than i would recommend that you replenish with fluids (water & /or gatorade - or other electrolyte replacement water based beverage) and a light meal - like broths/ jello. This will allow you to get your nutrition while allowing your bowel to rest.