As a general guideline, it is recommended to start by giving your dog a very small amount of apple cider vinegar diluted with water (like a teaspoon per 8 ounces of water) on an empty stomach. If your dog tolerates this amount, you can gradually increase it to 1 teaspoon per 4 ounces of water once or twice a day.
It is important to monitor your dog's response to apple cider vinegar to make sure they do not experience any negative effects. If you have any concerns, consult with your veterinarian before giving your dog apple cider vinegar.