Cut the chicken breasts into 1-inch chunks and place in a bowl. Seed and cut the red bell pepper into 1/2-inch pieces, then do the same with the green bell pepper. Dice the onion into similar-sized pieces so everything cooks evenly. Drain the pineapple chunks if they're packed in syrup, reserving about 2 tablespoons of the juice to add to your sauce later. Having everything prepped and ready before you start assembling packets makes the process much smoother and ensures even cooking throughout.

In a bowl, whisk together the teriyaki sauce, sesame dressing, garlic powder, and ground ginger until well combined. If you reserved pineapple juice from Step 1, stir it in now—this adds extra sweetness and helps the sauce coat the chicken better. I like to taste the sauce at this point and adjust the seasoning if needed; sometimes I add a splash more teriyaki if it needs more savory depth.

Preheat your grill to medium-high heat (around 400°F if using a gas grill). While it heats, tear off four large sheets of heavy-duty aluminum foil, each about 12 inches long. Fold each sheet in half to create a double layer, which prevents punctures and helps with heat distribution. Place the foil sheets on a flat work surface, ready for assembly.

Divide the prepared chicken chunks equally among the four foil sheets, placing them slightly off-center on each sheet. Distribute the red bell pepper, green bell pepper, onion, and pineapple chunks evenly across all packets. Pour about 1/4 cup of the sauce mixture from Step 2 over each packet. Fold the foil over the ingredients, then fold the edges tightly to seal, leaving a small air pocket inside for steam circulation—this creates a moist, tender result. I always double-check that the seals are tight by pressing along the edges firmly.

Carefully place the sealed foil packets on the preheated grill. Grill for 10-15 minutes, flipping each packet halfway through (around the 5-7 minute mark) to ensure even cooking. The packets will puff slightly as steam builds inside—this is what you want. The chicken is done when it reaches an internal temperature of 165°F; you can check this by carefully opening one packet and using an instant-read thermometer.

Remove the packets from the grill and let them cool for about 2 minutes so the steam can escape safely. Carefully open each foil packet (watch out for the hot steam) and transfer the contents to a serving plate or bowl. Garnish each portion generously with fresh cilantro and sesame seeds for a fresh, nutty finish that complements the sweet and savory flavors beautifully.