Combine honey, orange zest, orange juice, soy sauce, garlic, ginger, vinegar and crushed red pepper in a small bowl.
Coat a 5- to 6-quart slow cooker with cooking spray. Add drumsticks, pour in the sauce and mix to coat. Cover and cook until an instant-read thermometer registers 165°F when inserted into the thickest part of the meat without touching bone, 2 to 3 hours on High or 4 hours on Low.
Transfer the drumsticks to a bowl. Very carefully pour the liquid from the slow cooker into a medium skillet. Bring to a boil over high heat. Boil until reduced and syrupy, 10 to 15 minutes. Pour the sauce over the drumsticks and stir to coat. Serve sprinkled with cilantro and sesame seeds.