8-9yr old Rotti, extreamly sick. Unable to keep down food/water. Been to the vet with negative results HELP?

Its never any fun having a sick dog. The costs add up quickly. Your vet is correct that the next step is to do a x-ray with a contrast solution to see any changes in her gut. Try removing fluids for afew hours to slow down her gut. Then try a child's drink like Gator-Aid something that has the electrolytes in it. Even something sweet like a punch. Give her only a small amount and take it away then in an hour try another lap of fluid. Your only options is to return her to the vet and spend the money to find out what is going on. Most important is to not let her suffer if treatment is not an option .