In a small bowl, combine the brown sugar, ketchup, soy sauce, chicken broth, apple cider vinegar, ginger and garlic.
Place the chicken thighs in a shallow dish large enough that they can be laid in a single layer. (You can also place them in a ziplock bag.)
Reserve 1/2 cup of the marinade, and add the rest to the dish with the chicken thighs. Turn to coat the chicken in the sauce.
Cover the dish and refrigerate for 8 hours, or overnight.
When ready to make the chicken, remove it from the refrigerator and let it sit at room temperature for 30 minutes.
Preheat a grill to medium heat.
Grill the chicken until it reaches 170ºF, about 12-16 minutes, turning a few times during the cook time. Baste the chicken with the reserved marinade during the last 5 minutes of cook time.
Notes
*If possible, turn the chicken a time or two during the marinating time.Nutrition information provided as an estimate only. Various brands and products can change the counts. Any nutritional information should be used as a general guideline. Nutrition information is calculated making 12 buns from the recipe.