Cook the rice: Prepare white or brown rice according to package directions. Fluff and set aside.
Prep the sauce: In a small bowl, whisk soy sauce, water, honey, rice vinegar, sesame oil, ginger, and garlic.
In another small bowl, mix cornstarch with water to make a slurry. Set both aside.
Blanch or steam the veggies: Steam broccoli until crisp-tender, 3–4 minutes. Sauté bell pepper and carrot in a splash of oil for 2–3 minutes until just tender.
Season lightly with salt and pepper. Set aside.
Cook the chicken: Pat chicken dry and season with salt and pepper. Heat oil in a large skillet over medium-high.
Add chicken in a single layer and cook 5–7 minutes, stirring occasionally, until browned and cooked through.
Sauce it up: Lower heat to medium. Pour in the teriyaki sauce. Simmer 1–2 minutes, then stir in the cornstarch slurry.
Cook, stirring, until the sauce thickens and coats the chicken, about 1–2 more minutes. If too thick, add a splash of water.
Assemble bowls: Divide rice among 4–5 meal prep containers. Top with teriyaki chicken and an even mix of veggies.
Sprinkle with green onions and sesame seeds if using.
Cool and store: Let bowls cool to room temperature (no more than 1 hour) before sealing and refrigerating.