Trim chicken thigh fillets of extra fat, Rinse and drain well. Pat dry and cut into 1-inch strips. Season with salt and pepper to taste.
In a bowl, combine mango nectar, barbecue sauce, and red pepper flakes. Stir until well-distributed.
Add chicken and marinate in the refrigerator for at least 4 hours or overnight. Drain from marinade, reserving liquid.
In a saucepan over medium heat, simmer mango nectar-barbecue marinade for about 20 minutes or until reduced to about 1/2 cup.
Add sesame oil and stir to combine. Set aside.
Thread 2 to 3 chicken slices into each skewer.
Grill skewers on a hot grill for about 2 to 3 minutes each side. When the meat starts to lose its pink, baste with sweet mango mixture. Continue to grill and baste, turning on sides, until cooked through.
Remove from heat and serve hot.