Whisk coffee, vinegar, oil, sugar, garlic, peppercorns and salt in a glass dish large enough for meat to lie flat. Add steak and turn to coat. Cover and refrigerate for at least 1 hour or up to 8 hours.
Heat grill to high.
Remove steak from marinade (discard marinade). Lightly oil grill rack (see Tip). Place steak on grill and cook for 4 to 5 minutes per side for medium-rare. Transfer steak to a cutting board and let rest for 5 minutes. Slice thinly across the grain and serve.
To oil a grill rack: Oil a folded paper towel, hold it with tongs and rub it over the rack. Do not use cooking spray on a hot grill.