Make the sauce: In a small bowl, whisk soy sauce, rice vinegar, honey, water, and cornstarch until smooth. Stir in sesame oil and a pinch of red pepper flakes if using.
Set aside.
Prep the chicken: Pat the chicken dry and season lightly with salt and pepper. Cutting into even pieces helps it cook quickly and stay tender.
Steam or blanch the broccoli: Steam for 3–4 minutes until bright green and crisp-tender. If blanching, boil for 2 minutes, then drain and rinse under cold water.
Set aside.
Sauté aromatics: Heat the oil in a large skillet over medium-high heat. Add garlic and ginger; cook for 30 seconds until fragrant, stirring often to avoid burning.
Cook the chicken: Add the chicken to the skillet. Cook for 6–8 minutes, stirring occasionally, until browned and cooked through.
Add the sauce: Reduce heat to medium.
Whisk the sauce once more, then pour it into the pan. Stir as it thickens, about 1–2 minutes. If it gets too thick, add a splash of water.
Toss in the broccoli: Add the broccoli to the skillet and fold gently to coat everything in the sauce.
Taste and adjust seasoning with pepper or a touch more vinegar for brightness.
Assemble meal prep bowls: Divide the chicken and broccoli into 4–5 containers. Add 1/2 cup cooked brown rice or a generous portion of cauliflower rice if desired. Garnish with sesame seeds and green onions.
Cool before sealing: Let containers cool for 10–15 minutes before closing to prevent condensation and soggy texture.