dd soy sauce, garlic, brown sugar, and apple cider vinegar to a small pot. Bring to a boil then simmer over low heat for 2 minutes. Remove from heat and pour the marinade into a heat-safe container. Reserve until cool: 70*F or lower.
Stir fresh pineapple juice into chilled marinate, then pour into a large ziplock bag. Add steak to bag, squeezing out any air. Refrigerate for a minimum of 2 hours or overnight.
20 minutes before cooking, remove steaks from marinade. Set on a plate to come to room temperature for at least 20 minutes.
Heat grill or grill pan to high. Grill steaks for approximately 5 minutes per side.
Transfer steaks to a platter and tent with foil to let rest for 5 minutes. Serve with Grilled Pineapple slices , if desired.