Labradoodle & Goldendoodle Forum
I would try spraying it with Bitter Apple right before going out for a walk. I also wouldn't leave it on him when he isn't on a walk. When walking, each time he starts to try and take the leash to chew I would stop and correct him with a no chew. When he isn't chewing I would say "Good Boy, No Chew" and give him a treat. Or if he has a favorite toy that he likes to carry, let him carry it on the walk.
He may also be teething, and chewing helps relieve his sore gums. Make sure he has plenty of good safe chew toys.
One thing that may help: Take an old washrag, soak it in water, wring it out, tie it in a big knot, and put it in the freezer. That's been helpful for me with teething puppies in the past. Be sure to supervise him when you give it to him to chew.