Anytime I have a dog that has a UTI, I add extra water to their food. I also give Cranberry pills. I sometimes give Vitamin C but that is based on the ph level of the urine and the recommendation of the vet. My dogs rarely have crystals but perhaps I catch the UTIs early.
It seems like rescues I get from shelters almost always have UTIs. I think they get it from either holding it too long because they do not want to get their kennel dirty or because they eat dry food and drink water separately.
Jennifer