[header] How to stop vomiting when you have the stomach flu [title] Drink a small amount of water. [step] Vomiting can cause dehydration; because of this, you need to replace the fluid you have lost with water. Keep in mind that you should only take small sips of water because if you gulp down a big glass and expand your irritated stomach, you could end up vomiting again. 
[substeps] Take small sips of water every 15 minutes after you have vomited. Do this for three or four hours to hydrate yourself.