Cook the grains: Prepare brown rice, jasmine rice, quinoa, or cauliflower rice. Fluff and set aside.
Prep the veggies: Chop broccoli, bell peppers, and carrots into bite-size pieces.
Steam, sauté, or roast until crisp-tender. Season lightly with salt and pepper.
Make the sauce base: In a bowl, whisk soy sauce, water, maple syrup, rice vinegar, sesame oil, garlic, ginger, and red pepper flakes (if using). Set aside.
In a separate small bowl, stir together cornstarch and cold water to make a slurry.
Season the chicken: Pat chicken dry and season with a pinch of salt and black pepper.
Sear the chicken: Heat oil in a large skillet over medium-high. Add chicken in a single layer. Cook 5–7 minutes, stirring occasionally, until just cooked through and lightly browned.
Add the sauce: Reduce heat to medium.
Pour in the sauce base and bring to a gentle simmer for 1–2 minutes.
Thicken: Stir the cornstarch slurry, then stream it into the skillet while stirring. Simmer 1–2 minutes more, until glossy and slightly thick. If it gets too thick, add a splash of water.
Taste and adjust: Add a squeeze of lime or a splash more vinegar if you want extra brightness.
Adjust salt or sweetness as needed.
Assemble: Divide rice among 4–5 meal prep containers. Add a portion of veggies and top with teriyaki chicken. Sprinkle with sesame seeds and green onions.
Cool and store: Let containers cool uncovered for 15–20 minutes, then seal.
Refrigerate up to 4 days.