01 - Pat the chicken thighs completely dry using paper towels to ensure proper seasoning adhesion and crisping.
02 - In a large mixing bowl, whisk together olive oil, apple cider vinegar, brown sugar, smoked paprika, garlic powder, onion powder, chili powder, salt, and black pepper until the sugar dissolves.
03 - Add chicken thighs to the bowl and toss thoroughly to coat each piece evenly. Let marinate for at least 15 minutes, or refrigerate up to 4 hours for deeper flavor penetration.
04 - Preheat grill to medium-high heat or set oven to 400°F.
05 - Place chicken thighs skin-side down on the grill. Cook for 6-7 minutes until skin marks develop, then flip and brush generously with BBQ sauce.
06 - Continue grilling for 25-30 minutes, turning and basting with additional BBQ sauce every few minutes, until internal temperature reaches 175°F and skin is slightly charred. For oven method, place on foil-lined baking sheet skin-side up and roast for 30-35 minutes, brushing with sauce every 10 minutes.
07 - Remove from heat and let chicken rest for 5 minutes to allow juices to redistribute. Serve with extra BBQ sauce on the side.