Preheat the oven to 250°F. Line a shallow baking pan with foil and set a wire rack inside. Coat both with nonstick spray and set aside.
Place the baking powder and salt in a food storage bag and shake to combine. Add the drumettes, shake until coated and transfer them to the prepared rack.
Bake the drumettes for 30 minutes, then raise the oven temperature to 425°F and cook for 45 to 50 minutes more. About midway through the cooking time, turn the individual drumettes over and rotate the baking pan in the oven to ensure even browning.
While the drumettes bake, make the sauce. Heat the sesame oil in a small saucepan over medium heat. Add the garlic and sauté until fragrant and softened, 2 minutes.
Add the orange juice, soy sauce, sriracha, vinegar and brown sugar and increase the heat to medium-high. Continue cooking, stirring frequently, until the sauce has thickened to a syrupy consistency, 3 to 4 minutes.
Transfer the sauce to a large bowl, add the drumettes and toss until well coated. Return them to the wire rack and brush them with the remaining sauce. Sprinkle with sesame seeds, then turn the oven off and put the drumettes back in for 5 to 7 minutes to set the glaze. Serve immediately.