Most all sugar-free mints & gum are artificially sweetened and contain carbs. Even for those that say <1 carb on the label, it should actually be counted as 1 carb. If you do chew gum or mints, be sure to count the carbs into your daily carb intake & beware, those pieces of gum & mints can really add up quickly!
I found some cinnamon-oil infused toothpicks at Whole Foods this summer & stocked up on them. Zero carb, zero calorie, but they tingle in your mouth & help somewhat with breath.
I would think you can make your own pretty easily too... would need to find a good cinnamon essential oil (food grade) or maybe extract could work too?