Cats are generally thought of as rather low-maintenance pets, able to take care of themselves for the most part--and generally preferring it that way! However, even the healthiest cats are threatened by a variety of potential ill-health conditions, particularly later in life.
Cystitis, cat acne, fleas, ticks, FIV, bald spots, mites, and ear issues are just the start of a long list of common conditions that might afflict your pet.
As with their human owners, apple cider vinegar is often a popular remedy for cat ailments of several kinds. Cats will often take a small dose added to their food or water (try one if your cat rejects the other).