In a small bowl, whisk soy sauce, water, brown sugar, honey, rice vinegar, sesame oil, and sriracha. In a separate cup, mix cornstarch with cold water until smooth. Keep both nearby.
Set a large skillet or wok over medium-high heat. Add 1 tablespoon oil. When it shimmers, add onion and bell pepper. Stir-fry 2–3 minutes until slightly softened but still crisp. Transfer to a plate.
Add 1–2 tablespoons water to the hot pan, toss in broccoli, cover for 1–2 minutes to steam, then uncover and stir until bright green and tender-crisp. Transfer to the veggie plate.
Add remaining oil. Crumble in ground turkey. Season lightly with salt and pepper. Cook 4–6 minutes, breaking it up, until well-browned with caramelized bits. Don't overcrowd or over-stir—color equals flavor.
Stir in garlic, ginger, and the white parts of the scallions. Cook 30–45 seconds until fragrant (do not scorch).
Return veggies to the pan. Pour in the teriyaki base and bring to a simmer. Whisk the cornstarch slurry and add it in, stirring constantly. Cook 1–2 minutes until the sauce thickens and coats everything.
Need salt? Add a splash more soy. Sweeter? A drizzle more honey. More heat? Sriracha. Finish with scallion greens.
Spoon over rice or noodles. Garnish with sesame seeds and a squeeze of lime for brightness. Eat immediately while it's glossy and perfect.