Marinate chicken. In a large bowl, whisk together barbecue sauce, crushed pineapple, and cilantro. Add diced chicken breast, tossing until every piece is coated in the pineapple BBQ marinade. Cover and refrigerate for at least 30 minutes, or up to overnight for extra flavor.
Prepare vegetables. While the chicken marinates, chop onion and pepper into large chunks. Separate the layers of the onion.
Assemble skewers. Alternate pieces of marinated chicken, onion layers, and pepper chunks on the skewers. Pack them close, leaving about 2 inches free on each end for easy handling and eating.
Smoke chicken kebabs. Preheat the smoker to 250°F. Place the skewers on the grill grates. After 1 hour, flip them. Continue smoking until the chicken reaches an internal temperature of 165°F. This usually takes about 2 hours. You can increase the heat to 350°F after flipping if you want them to finish faster, but I prefer low and slow.
Serve. Remove skewers from the grill, sprinkle with diced green onion or chives, and serve immediately.
