I think you need to go see the vet about a UTI... and then you could give the ACV LATER as a preventative. It won't hurt. My dogs get ACV occasionally in raw meals for digestion reason. I, myself, drink 2 tbls. a day mixed in water. There are a lot of "things" it is naturally helpful for.
Again, GO TO THE VET. UTI = nothing to mess around with.
edit: apology from miss bossy britches because I see you already ARE going to the vet. All I meant was that it shouldn't be used in lieu of a possible antibiotic.