Soak wooden skewers in water for a few hours if using wooden skewers; this prevents burning on the grill.
Preheat your outdoor grill to medium-high heat (gas or charcoal) while you prepare the ingredients.
Thread the chicken chunks, yellow pepper, red pepper, red onion, and pineapple onto the skewers, alternating pieces evenly; set the assembled skewers aside.
Make the teriyaki sauce: in a small saucepan combine soy sauce, water, cornstarch, sesame oil, garlic powder, ground ginger, brown sugar, and honey; whisk until smooth.
Bring the sauce to a boil over medium heat, then reduce heat and simmer gently until it thickens slightly, about 2–4 minutes; remove from heat and stir in sesame seeds.
Place the skewers on the hot grill and baste with teriyaki sauce; grill for about 3–4 minutes per side, continuing to baste, until the chicken is cooked through and reaches 165°F (74°C).
If you plan to serve extra sauce with the cooked skewers, return the reserved sauce to a simmer for at least a minute to bring it back to a boil before using.
Remove skewers from the grill and let rest briefly before serving over brown rice if desired.