01 - If using wooden skewers, submerge them in water and soak for at least 30 minutes to prevent burning on the grill.
02 - In a mixing bowl, whisk together the soy sauce, brown sugar, rice vinegar, sesame oil, minced garlic, ginger, gochujang, and honey until smooth and well combined. Reserve 1/4 cup of the sauce for basting during grilling.
03 - Place the chicken pieces in a large bowl and pour the remaining sauce over them. Toss to coat evenly, cover, and refrigerate for at least 30 minutes or up to 2 hours for more intense flavor.
04 - Thread the marinated chicken pieces onto the skewers, alternating with chunks of red bell pepper, yellow bell pepper, and red onion. Lightly brush the assembled skewers with vegetable oil.
05 - Preheat an outdoor grill or grill pan to medium-high heat, approximately 400°F.
06 - Place the skewers on the hot grill and cook for 10 to 12 minutes, turning occasionally. During the last few minutes of cooking, brush generously with the reserved BBQ sauce. Cook until the chicken reaches an internal temperature of 165°F and develops a lightly charred exterior.
07 - Transfer the grilled skewers to a serving platter. Sprinkle with toasted sesame seeds and finely sliced green onion. Serve immediately while hot.