How much Vitamin C can i give to my dog?

My dog has a UTI and were trying to go the herbal route for reasons on antibiotics and the negative effects it has on his body. He's a 45lb lab mix and i've read that the bacteria doesn't like the acidic effect of orange juice and vitamin c, along with cranberry juice, blueberry juice, and pink grapefruit juice. I'm not sure how much vitamin c is appropriate for a dog, would anyone know?

dogs dont need C, as they make their own C from the foods they eat. Any extra will not be beneficial, as its water-soluable and will just be flushed out of the system.If your dog has a UTI, he needs antibiotics from the vet.. not "herbal" remedies. Cranberry is good to help prevent UTIs, but NOT a cure.