Step 1: Prepare the Marinade : In a saucepan, combine soy sauce, brown sugar, honey, vinegar, sesame oil, garlic, and ginger. Bring to a gentle simmer over medium heat, stirring occasionally until sugar dissolves. Mix cornstarch and water in a small bowl, then stir into the sauce. Simmer for 1–2 minutes until slightly thickened, then remove from heat. Let it cool completely — this will be your marinade and glaze.
Step 2: Marinate the Beef : Place beef cubes in a large bowl or zip-top bag. Pour half of the cooled teriyaki sauce over the beef (reserve the other half for basting/glazing). Toss to coat evenly and marinate in the refrigerator for 1–2 hours (or up to 6 hours for extra flavor).
Step 3: Prepare the Skewers : If using wooden skewers, soak them in water for at least 30 minutes to prevent burning. Thread beef cubes, pineapple chunks, and red bell pepper pieces alternately onto the skewers. Discard any marinade that touched raw beef.
Step 4: Grill the Skewers : Preheat grill (or grill pan) to medium-high heat (400–425°F / 200–220°C). Brush the grates lightly with oil to prevent sticking. Place skewers on the grill and cook for 8–12 minutes total, turning every few minutes to cook evenly. During the last few minutes, brush the reserved teriyaki sauce over the skewers to glaze them beautifully.
Step 5: Serve and Garnish : Remove from the grill and rest for 2–3 minutes. Sprinkle with toasted sesame seeds and chopped green onions. Serve hot — the glossy glaze, tender beef, and sweet pineapple make this dish shine.