Cook the rice. Prepare your rice according to package directions.
Keep it warm and fluffy. Leftover day-old rice also works well if you reheat it gently.
Whisk the sauce base. In a bowl, combine soy sauce, mirin, honey (or sugar), rice vinegar, ginger, garlic, and water. Set aside.
In a separate small cup, stir together cornstarch and water to make a smooth slurry.
Prep the chicken and veggies. Pat the chicken dry and cut it into bite-size pieces. Slice the bell pepper and chop the broccoli into small florets so they cook quickly and evenly.
Sear the chicken. Heat oil in a large skillet over medium-high. Add the chicken in a single layer and let it brown for 2–3 minutes before stirring.
Cook until nearly cooked through, about 5–6 minutes total. Season lightly with a pinch of salt if using low-sodium soy.
Stir-fry the vegetables. Push the chicken to one side. Add a little more oil if needed.
Toss in broccoli and bell pepper. Stir-fry for 2–3 minutes until bright and slightly tender but still crisp.
Add the sauce. Pour in the teriyaki sauce base. Bring it to a simmer, then stir in the cornstarch slurry.
Cook 1–2 minutes, stirring, until the sauce thickens and coats the chicken and vegetables. Stir in the sesame oil if using.
Taste and adjust. Check seasoning. Add a splash of water if the sauce is too thick, or a touch more honey if you prefer sweeter.
For extra gloss, let it bubble for another 30 seconds.
Assemble the bowls. Spoon rice into bowls. Top with the teriyaki chicken and veggies. Sprinkle with sesame seeds and green onions.
Add optional toppings like a fried egg or steamed edamame.
Serve hot. Enjoy right away for the best texture and shine.