Combine brown sugar, worcestershire sauce, tomato sauce, ketchup, chili powders, cider vinegar and water and mix well. Set aside.
In a large skillet over medium, heat oil to shimmering. Add onion and saute until translucent.
Add ground turkey and saute, breaking up with spatula into small pieces. Cook until almost no pink remains.
Add sauce and bell pepper to skillet and cook, uncovered, stirring occasionally until slightly thickened and heated through, about 10-15 minutes.
Serve on buns.