In a large resealable plastic bag, combine brown sugar, soy sauce, V8 juice, olive oil, chili powder, garlic and cumin.
Add steak and marinate in refrigerator at least 8 hours or overnight.
Remove steak from bag and discard marinade.
Heat a gas grill to medium-high or a charcoal grill to medium-hot coals. Grill steak for 5 to 6 minutes per side, until internal temperature registers 140° on an instant-read thermometer. Remove steak from grill and cover with foil. Let rest 5 minutes before thinly slicing against the grain. Meanwhile, grill peppers, zucchini, onion and tomatoes, if desired. Serve sliced steak with warmed corn tortillas and grilled vegetables, if desired.
