In a small bowl, whisk together the olive oil, lime juice, chopped cilantro, minced garlic, sugar, salt, and pepper until combined.
Place the chicken in a large zipper bag or a shallow dish and pour the marinade over it, ensuring all pieces are coated.
Seal the bag (or cover the dish) and refrigerate for 30 minutes up to 8 hours to marinate.
About 10 minutes before grilling, preheat the grill to medium–medium-high (about 400°F) and oil the grate lightly.
Remove chicken from the marinade and place on the hot grill. Grill 5–7 minutes per side, flipping once, until an instant-read thermometer inserted into the thickest part reads 165°F.
Transfer the chicken to a plate and let rest for 10 minutes before serving.