People have used vinegar for centuries as a health treatment and household cleaning agent. Fans of apple cider vinegar (ACV) claim it is a natural preservative, disinfectant, and source of nutrients. Apple cider vinegar is an excellent supplement to add to your dog’s diet. Anecdotally, it is said to help improve digestive health, control pests, and clear up skin and ear infections. While modern medicine does not recognize apple cider vinegar as effective, some veterinarians will suggest its use in moderation. Apple cider vinegar is not an instant fix, nor is it without its possible side-effects.