The ACV works and one should remember everything in moderation. You may have given too much as it is oly 1 tsp for 50 lb dog and one should use it on and off not steady for 3 straight months. Foods have also caused UTI's.
My dog had some signs of allergies (runny eyes, flaky skin) that were not helped by the vet's suggestions, so I did a web search and found the "ACV for dogs" site. It sounded like a harmless and potentially helpful remedy, so I tried it. It didn't do a thing for the allergic symptoms, and 3 months later, my (spayed) dog developed a bloody discharge from her urinary tract. Lab tests diagnosed struvite crystals in her bladder, which, the vet said, form when the urine is too alkaline. Some research informed me that apple cider vinegar has an alkalinizing effect in the body! After immediate cessation of the apple cider vinegar and a month of a prescription urinary acidifier, my dog's urine is now testing normal. Naturally, after this experience, I do not recommend apple cider vinegar for dogs.