1. Preheat grill to high heat. Combine black pepper, salt, and ground red pepper; sprinkle over chicken drumsticks. Place drumsticks on grill rack coated with cooking spray. Cover and grill 3 minutes or until charred; reduce heat to medium. Grill 18 minutes or until a thermometer inserted into the thickest part registers 160°, turning occasionally.
2. Combine Sriracha, chicken stock, lime juice, ginger, sugar, and garlic. Serve sauce on the side for dipping.