first got to the drug store or or store period..go to the baby section and purchase this liquid called Pedilyite. it is good for dehydration. which sounds like you have. you need electrolytes and that contains it. its for babies but your ok with it. its #1 recommended by pediatricians and dr.s, i use to give it to my baby.
Seriously, this is gonna sound quite wrong, BUT, one time I was in your exact situation, I couldn't keep ANYTHING down for longer than 30 seconds......needless to say I was BEYOND mad about this and sick of vomiting, so, I got the largest glass of ice water I could find, then I went outside and CHUGGED as much as I could.....then I OBVIOUSLY threw it right back up, but the it felt good throwing up that cold water instead of just dry heaving and having it hurt.....so I did the cold water thing a couple few times and I don't know why but I stopped having the urge to vomit, then a bit later I ate some soup and it stayed down......and I slowly worked up to soup and crackers and then it was all good.....I ain't sayin it's gonna work for you for sure, but it surely can't hurt too much.....good luck!!!