Heat the picante sauce, vinegar and brown sugar in a 3-quart saucepan over medium-high heat to a boil.Add the chicken to the saucepan. Reduce the heat to low. Cover and cook for 30 minutes or until the chicken is fork-tender.  Uncover and cook for another 30 minutes.Remove the chicken from the saucepan to a cutting board. Using 2 forks, shred the chicken. Return the chicken to the saucepan and cook for 15 minutes or until the sauce mixture is thickened, stirring occasionally.  Divide the chicken mixture among the buns. Sprinkle with the cheese.