Cut the chicken breasts into tender sized strips and place them in a bowl or into a freezer bag. Add in the soy sauce, rice vinegar, ground ginger and garlic powder, salt and pepper, maple syrup, and olive oil. Massage the marinade into the chicken and let it sit on the counter for 15-30 minutes.
Preheat the oven to 400° F. and line a sheet pan with parchment paper or foil. If using foil spray it with cooking spray.
While the chicken marinates cut the brussels sprouts in half and place them on one half of the sheet pan. Drizzle with olive oil and sprinkle with salt and pepper. Toss them until they're coated and then arrange them cut side down on the sheet pan. Roast for 6-7 minutes then remove the pan from the oven.
Remove the chicken from the marinade and pat off any excess marinade with paper towels. Place the chicken on the other half of the sheet pan and put it back in the oven. Roast for 10 minutes.
Meanwhile, make the teriyaki sauce. In a small saucepan combine the soy sauce, rice vinegar, maple syrup, water, ground ginger, garlic powder, and sriracha. Whisk together and bring to a boil.
Once the sauce is boiling whisk in the cornstarch slurry. Lower the heat and stir until the sauce starts to thicken. Once it's thick enough to coat the back of a spoon, turn off the heat.
Remove the chicken and brussels sprouts from the oven and brush some of the teriyaki sauce on top of the chicken. Put it back in the oven and continue to cook until the internal temperature of the chicken reaches 165° F.
Remove the sheet pan from the oven and brush the chicken with additional teriyaki sauce if desired. Serve on top of rice with extra sauce, sesame seeds, and sliced green onions.