Hartz sells breath strips for dogs. They are just like listerine pocket packs, but these are for dogs and they work too.
I have a Basset Hound who sometimes gets bad breath. When he does, it is usually because of tartar buildup, so we use dog toothpaste and brush his teeth with a dog toothbrush. It clears his bad breath right up.
Our dog is a Golden Retriever. He has had bad breath on occasion. We brush his teeth and try and clean his tongue. We also have replaced canned food with dry food; it doesn't stick to the teeth. We have tried the dental bones and they work okay. Also, the pet grass has helped with his digestive system, which in turn has helped the gasses from his stomach.
I have a Labrador and we use the milk bone brand dog treats that are for bad breath. The other thing we have done is give him citrus once in awhile, either a few orange slices are lemon wedges. He loves them and I think that acid helps to break down some of the plaque in his mouth that causes bad breath.
Dogs usually don't have bad breath if their teeth are clean. The best remedy is brushing your dog's teeth a minimum of a couple of times a week. However, if your dog has advanced tarter and plaque, he'll need to go to the vet for a dental cleaning. To help keep your dog's teeth clean in between brushings try getting your dog to eat raw carrots. They work well at keeping your dog's back teeth clean, they are inexpensive and, if your dog likes them, it's a healthy treat and a wonderful substitute for biscuits if your dog is overweight. If you can't get your dog to eat carrots, your local pet store will carry a variety of dental chews in a variety of flavors. Also, if you feed your dog canned food you may wish to consider changing his diet to dry food.
also see A Guide to Pet Dental Care Services
also see Guide to Dog Teeth: Care and Cleaning
also see Dog Breath Treats: Which Ones Actually Work?
also see Preparing Your Puppy for a Dental Exam
also see Canine Dentistry: Ensuring the Best Care
also see Removing Dog Drool From Upholstery
also see What Causes Bad Breath In My Dog?
also see Dental Problems in Dogs