1. Score steaks on both sides in a diamond pattern using a sharp knife.
2. Sprinkle garlic powder, salt and pepper over both sides of steaks and rub.
3. Place steaks in a shallow dish and pour cola over them.
4. Cover and marinate 2-4 hours, turning steaks over every hour; during the last hour, coat the steaks with a thin layer of BBQ sauce.
5. Preheat grill to high heat.
6. Lightly oil grill grate; place steaks on grill and sear on both sides over high heat, about 4 minutes per side.
7. Reduce heat to medium-low, cover, and slow-cook 10 minutes per side.
8. Spread a thin layer of remaining BBQ sauce over the steaks during the last few minutes of cooking and allow it to cook until dry for a glazed effect.