Preheat oven to 400°F. Line a large baking sheet with heavy duty foil. Spray with cooking spray.
Place brussel sprouts in a large mixing bowl, Drizzle with 3 Tbsp bacon drippings, salt and black pepper. Toss to coat. Arrange cut side down on pan. Place into oven and bake for 10 minutes.
Meanwhile, in a measuring cup or bowl, whisk together reserved 1 Tbsp bacon drippings, maple syrup, teriyaki, brown sugar, garlic and onion powders with red pepper flakes. Mix until brown sugar has dissolved.
Lower oven temperature to 375°F. Remove brussel sprouts from oven, drizzle with maple glaze. Stur until coated and return to oven for another 10-15 minutes. Increase the oven temperature to broil in the last 5 minutes. Broil until lightly charred. Don't walk away.
Serve immediately topped with crumbled cooked bacon and drizzled with pan juices.