Apple cider vinegar is totally safe for your dog. It is rich in iron, magnesium, and potassium, and it's good for your dog’s digestive system. So, even if your dog licks apple cider vinegar, it is going to be beneficial for it. But please remember that consuming too much apple cider vinegar can upset your dog's stomach. Moreover, apple cider vinegar is acidic by nature, and not all dogs can digest it. Hence, it can also lead to gastrointestinal complications in some dogs if consumed in large quantities.