Ginger is best to fight nausea. But if you can't stop vomiting, you should drink an electrolyte. One tablespoon per half hour. Try something simple like toast or saltines after you can control your vomiting. If not, keep up with the electrolytes.
My wife had this problem all through her first pregnancy. This is what we had to resort to. If it ever happens again, I'll definitely consider using cannabis.