Yes, you can. While most any vinegar works, most websites that suggest using vinegar as an insect repellent recommend using apple cider vinegar. However, I'd like to reiterate that this would only help against black flies, and not necessarily other biting flies like stable, deer, or horse flies. Learn more about the different flies that can bite dogs in Ontario here. Mix 1 part apple cider vinegar with 1 part water, give it a good shake and spray on your pup. Apply the vinegar to your pup's neck, collar, torso, tail, belly, or overall coat.