In a liquid measuring cup or small bowl, whisk all ingredients for teriyaki sauce together until smooth. Set aside.
Spray a large skillet with nonstick cooking spray and then add the olive oil. Preheat over medium heat. Sprinkle chicken with garlic powder, salt and pepper. Add to hot pan and cook, stirring frequently, until completely cooked through.
Once chicken is cooked, pour over teriyaki sauce liquid and bring to a simmer. As the sauce simmers, it will thicken. Once sauce has thickened, add more sesame seeds as garnish and serve with steamed broccoli and white rice.