Whisk together the brown sugar, soy sauce, minced garlic, grated ginger, lime juice, and optional chili flakes in a bowl to prepare the marinade.
Choose your cooking method: grill, bake, or slow-cook the chicken.
For grilling, cook the chicken on the grill for about 6-8 minutes per side, basting with leftover marinade. For baking, arrange in a baking dish, pour marinade over, and bake for about 30 minutes. For slow cooking, place chicken and pineapple in the slow cooker with marinade and cook on low for about 4-5 hours.
Garnish with fresh cilantro before serving.