To treat your dogs bad breath at home take some baking soda and water and make a natural dog toothpaste and then use a toothbrush to brush and clean your dogs teeth to remove any bacteria from the dogs teeth.
Then after brushing the dogs teeth with baking soda and water paste take some apple cider vinegar and dip a toothbrush in the apple cider vinegar and brush the dogs teeth again with the apple cider vinegar.
The apple cider vinegar will kill bacteria in the dogs mouth and on their teeth which is usually responsible for the bad dog breath.
I would also add some apple cider vinegar to the dogs water bowl as well so when they drink the water with the apple cider vinegar the apple cider vinegar will continue to keep the bacteria off the dogs teeth.
You can also feed the dog some parsley to help rid the dogs teeth and mouth of bacteria and help the dogs teeth and mouth smell better.
Or you can buy some dog treats that the dog can chew on and clean it's teeth while chewing on it.