1. Prepare the chicken: Start by cutting the boneless, skinless chicken breasts or thighs into 1-inch cubes. Try to make them as uniform in size as possible to ensure even cooking. Place the cubed chicken in a large bowl.

2. Make the marinade: In a separate medium bowl, whisk together the BBQ sauce, olive oil, apple cider vinegar, smoked paprika, garlic powder, onion powder, salt, and black pepper. Mix until all ingredients are well combined.

3. Marinate the chicken: Pour the BBQ sauce mixture over the chicken cubes in the large bowl. Toss everything together until the chicken is thoroughly coated. Cover the bowl and refrigerate for at least 30 minutes. For a deeper flavor, you can marinate the chicken for up to 4 hours. If using wooden skewers, remember to soak them in water during this time to prevent them from burning on the grill.

4. Prepare the grill: Preheat your grill to medium-high heat (around 400 F or 200 C). Lightly oil the grill grates to prevent sticking.

5. Assemble the skewers: While the grill is heating, thread the marinated chicken pieces onto the skewers. If you’re using optional vegetables, alternate chicken pieces with red bell pepper, green bell pepper, and red onion pieces. Don’t pack the chicken too tightly; leave a small space between each piece for even cooking.

6. Grill the skewers: Place the assembled skewers on the preheated grill. Cook for 10-15 minutes, turning them every 3-4 minutes, until the chicken is cooked through and has nice char marks. The internal temperature of the chicken should reach 165 F (74 C) when checked with a meat thermometer.

7. Serve immediately: Once cooked, remove the skewers from the grill and let them rest for a few minutes before serving. This allows the juices to redistribute, keeping the chicken moist and tender.