1. Redirect your dog's attention. When you see your dog chewing on the leash, immediately offer them something else to chew on, such as a toy or a chew bone. This will help to distract them from the leash and redirect their chewing behavior.
2. Use positive reinforcement. When your dog is not chewing on the leash, praise them and give them a treat. This will help them to associate good behavior with not chewing on the leash.
3. Use a bitter spray. There are a number of commercially available bitter sprays that you can use to deter your dog from chewing on objects. Simply spray the leash with the bitter spray and your dog will be less likely to want to chew on it.
4. Keep your leash out of reach. When you're not using the leash, keep it in a place where your dog can't reach it, such as a high shelf or a closet. This will help to reduce the temptation for your dog to chew on it.
5. Train your dog to "leave it." The "leave it" command can be a very helpful way to stop your dog from chewing on things they shouldn't. To teach your dog the "leave it" command, start by holding a treat in front of them. Then, say "leave it" in a firm voice and slowly move the treat away from them. If they don't try to take the treat, praise them and give them the treat. Repeat this exercise several times until your dog is consistently leaving the treat when you say "leave it." Once they have mastered this, you can start to use the "leave it" command to stop them from chewing on the leash.
6. Consult with a professional trainer. If you're having trouble stopping your dog from eating the leash, consult with a professional trainer. They can help you to develop a personalized training plan for your dog.