How can I hydrate my 6mnth old Beagle until tomorrow when I can take her back to the vet?

Instead of home remedies, take her to a doggy emergency room. She can go several days without food, but not very long without water. Like you said, the vet giving a dog fluids is a quick and not very distressing procedure. Have your regular vet address her underlying issues during regular business hours, but for now get some fluids in her. Best of luck. We'll keep our fingers crossed for Princess.