Dissolve Starbucks VIA in the warm water. You can also use ¾ cup strong brewed coffee or the equivalent amount of instant coffee used for an 8-oz. cup mixed with ¾ cup water.
Whisk together the VIA mixture, balsamic vinegar, olive oil, brown sugar, garlic, peppercorns and salt.
Lay steaks out flat in a rimmed dish and pour marinade over top. Cover and refrigerate.
Allow steaks to marinate for as little as one hour or up to 8 hours, turning occasionally.