Line your slow cooker with a liner or spray with non stick spray.
Place onion, celery and garlic in slow cooker. Place chicken on top of the vegetables. On top of the chicken add chili powder, brown sugar, vinegar, BBQ sauce, Worcestershire and sriracha.
Cover and cook on low 4-5 hours. Remove chicken from slow cooker and shred with 2 forks. Place chicken back into slow cooker (turned off), stir to coat with sauce and serve on toasted buns with cheddar cheese and cooked bacon if desired.
Alternately, serve chicken over rice, as a pizza topping or roll up in a tortilla!