3-Ingredient Simple Shampoo Dish detergent is formulated to cut through grease and will do a great job of washing away oils that accumulate on your dog’s coat and skin. White vinegar has antibacterial and deodorant properties and will leave his coat shiny and clean. Just be careful not to get any in his eyes.
2 cups of warm water
1/4 cup of nontoxic dish soap
1/2 cup of white vinegar
Combine all ingredients in a spray bottle and shake to mix. Then wet your dog’s coat with warm water and spray with shampoo, avoiding his eyes. Work the shampoo into his coat, creating a thick lather. Rinse thoroughly and repeatedly, even if you think all signs of shampoo are gone. Then dry him off, and he’s good to go! 
 Reisen, Jan. "Easy Homemade Dog Shampoo." American Kennel Club, 14 June 2021, https://www.akc.org/expert-advice/lifestyle/easy-natural-homemade-dog-shampoo/