Turn the Weber grill to medium-high heat.
Whisk brown sugar, vinegar, sambal, soy sauce, Sriracha, ginger and garlic in a large bowl. Once combined, divide equally into two bowls. Add chicken to one of the bowls and toss to coat. Let marinate for at least 30 minutes. Remove chicken and thread 4 or 5 pieces onto each skewer.
Transfer the other bowl of the marinade (without the chicken) to a small saucepan. Bring to a boil, reduce heat, and simmer until reduced by half, roughly 7–10 minutes.
Transfer the chicken to the grill, turning and basting often with reduced marinade, until cooked through, 8–10 minutes. Remove skewers and transfer to a serving platter. Sprinkle with the scallions and serve with lime wedges.