Hmmm, I don't know about orange or cranberry juice. Grape juice is definitely a no-no, though. For a urinary tract infection I'd definitely go to the vet, which will mean a course of antibiotics. You must be sure to give the entire course of antibiotics or they do more harm than good. Along with antibiotics, I'd feed some yogurt with active cultures to guard against losing the "good bacteria" necessary for a dog to be healthy and avoid yeast complications.
And plenty of fresh, clean water, preferably filtered.