Combine the brown sugar, whiskey, apple cider vinegar, olive oil, Better Than Bouillon, onion powder, garlic powder, rosemary, garlic, salt, and black pepper in a large glass measuring cup. Stir with a spoon to combine.
Place the steaks in a large zip-style freezer gallon bag and pour the marinade over steaks. Refrigerate for 4 to 24 hours. When ready to cook, allow the steaks to come to room temperature while preparing the grill.
Grill the steaks on medium-high heat for about 6 minutes on each side, or until desired doneness is reached. Transfer the steaks to a plate or half sheet pan lined with parchment paper or aluminum foil. Cover with aluminum foil to keep warm and allow to rest for 5 minutes.
Slice on a cutting board. Serve the steak over a fresh garden salad, or serve with seasonal vegetables, and mashed potatoes.