Hello and welcome to Just Answer. I have some questions for you to help me answer you better.
How old is your dog and what breed or guess what breed if she is a mix?
Other than leaving puddles when she lays down, does she have normal urinary patterns the rest of the time (no straining, red tinge to urine, increase in frequency)?
Thanks and I will help you soon!
The direct answer to your question is that you can give your dog cranberry juice, but it is impossible to give her enough to help if she has a bacterial infection in her urinary tract. The amount of cranberry juice she would have to drink is not something we can ever get a dog to do. That is the bad news. The good news is that you can give cranberry extract tablets and these are available at vitamin/supplement stores.
Given that there is no FDA regulation over "nutraceutical" products, it is impossible to know how the over the counter cranberry extract tablets will work as the amount of actual active ingredient in them varies tremendously. There is a veterinary product called Crananidin, made by Nutramax Labs that is very consistent in its formulation and has had clinical studies to back up it's effectiveness at decreasing the adhesion of bacteria to bladder wall cells. You can read more about it at www.nutramaxlabs.com
Given that she is just leaking and isn't having urgency, increase in frequency or other signs associated with a UTI, it is not likely that you are dealing with "just" a UTI. From what you describe it sounds more like incontinence, and treating that usually requires drugs that tighten the urethra. The most commonly prescribed drug is phenylpropanolamine, and it is a prescription.
I hope this helps you, and even though you don't want to see a veterinarian, you might have pretty good results if you have a vet look at her, look at her urine and then treat her appropriately.