Fixed this over the weekend, and my family went nuts for it!

Preheat your grill to medium-high heat.
Lay out the sheets of aluminum foil and lightly coat each with olive oil.
Place one chicken breast in the center of each foil sheet.

Divide the pineapple chunks, bell peppers, and onion slices evenly among the foil packets, placing them on top of the chicken.
Drizzle each packet with teriyaki sauce and season with salt and pepper.
Fold the sides of the foil over the chicken and vegetables, sealing the packets tightly.
Place the foil packets on the grill and cook for 20-25 minutes, or until the chicken is cooked through and the vegetables are tender.
Carefully open the packets (watch out for steam!) and serve hot.
Variations & Tips
For a spicier kick, add some sliced jalapeños or a sprinkle of red pepper flakes to the packets before sealing. If you prefer a different protein, shrimp or tofu can be great substitutes for chicken. For a more robust flavor, marinate the chicken in the teriyaki sauce for a few hours before assembling the packets. You can also add other vegetables like snap peas or broccoli for more variety.