Soak the skewers in water for at least 30 minutes.
In a medium saucepan, add olive oil, garlic and onion and place over medium heat. Saute for 2 to 3 minutes. When onions are soft and translucent, add remaining ingredients and season, to taste. Simmer for 5 minutes until thickened. Remove from heat and set aside
Skewer a tenderloin half on each of the soaked wooden skewers, keeping the tenderloin towards the end. Drizzle the chicken with olive oil and season with salt and pepper. Grill the skewers over medium heat. Cook for 2 minutes then turn each skewer over once and then brush on the reserved BBQ sauce. Cook for 2 to 3 more minutes until cooked through.