Add the brown sugar, vinegar, soda, garlic, soy sauce, and peppers. Stir to combine.
Cook on low for 6-8 hours or high for about 4 hours.
Make a slurry with the cornstarch and a couple of tablespoons of water. Stir the slurry into the sauce in the crockpot. Cook on high until the sauce has thickened.
Serve as whole chicken breasts or shred. It is great with rice or noodles so you can soak up some of the delicious sauce.