Serves 4

Adjust oven rack to highest position (about 5 inches from broiler element) and heat broiler. Set wire rack over rimmed baking sheet. Combine sugar, paprika, cumin, cayenne, and salt in large bowl. Add chicken and toss to coat. Thread seasoned chicken onto four 12-inch metal skewers.

Whisk ¾ cup barbecue sauce and 2 tablespoons vinegar in small bowl. In second bowl, combine sour cream, remaining barbecue sauce, and remaining vinegar; set aside for serving.

Brush each kabob with barbecue sauce-vinegar mixture. Broil until lightly browned, 5 to 7 minutes. Flip kabobs, brush with remaining sauce, and continue to broil until chicken is lightly charred and cooked through, 5 to 7 minutes. Serve with sour cream sauce.