In a medium bowl, stir together the olive oil, ranch dressing, rosemary, salt, lemon juice, white vinegar, pepper, and sugar. Let stand for 5 minutes. Place chicken in the bowl, and stir to coat with the marinade. Cover and refrigerate for 30 minutes.
Preheat the grill for medium-high heat. Thread chicken onto skewers and discard marinade.
Lightly oil the grill grate. Grill skewers for 8 to 12 minutes, or until the chicken is no longer pink in the center, and the juices run clear.