Whisk teriyaki sauce together in a bowl. Heat 2 tsp oil in 12-inch non-stick skillet over medium-high heat. Pat chicken dry with paper towels. Add half of the chicken to skillet, breaking up any clumps, and cook until lightly browned, about 5 minutes. Transfer to a plate. Repeat with 2 tsp oil and remaining chicken.

Add remaining 2 tsp oil, bell pepper, and jalapeno, if using to now- empty skillet and cook until just softened, about 3 minutes. Return chicken and any accumulated juices to skillet and toss to combine. Whisk sauce mixture to reconstitute, then add to skillet and cook, stirring constantly, until slightly thickened, about 1 minute. Garnish with green onions and serve.

Enjoy!