Grilled Coffee & Cola Skirt Steak

Ingredients:

1 whole beef skirt steak, about 1 1/4 pounds (no need to trim, except for any obvious large chunks of fat)
salt and cayenne to taste
For the marinade:
2-3 cloves minced garlic
2 tbsp ketchup
1 1/2 tsp freshly ground black pepper
1 tsp salt
1 tsp dried rosemary (or 1 tbsp freshly minced)
1/4 tsp hot sauce, or to taste
1/4 cup rice vinegar
1/2 cup strong, freshly brewed coffee
1 (12-oz) bottle cola