2 tablespoons low-sodium soy sauce
1 tablespoon brown sugar, light or dark
1 tablespoon extra virgin olive oil
1/2 teaspoon finely minced garlic
1 teaspoon Dijon mustard
1 pound sirloin steak, cut into 1-inch cubes
In a large bowl or plastic container, mix together the soy sauce, olive oil, mustard, brown sugar and garlic until well blended.
Add the beef cubes and toss in the mixture to coat. Marinate in the refrigerator for at least 2 hours, or up to overnight.
Soak 8 12-inch wooden skewers in water to cover for at least 30 minutes.
Preheat the broiler or grill. Skewer the sirloin cubes, dividing them evenly between the skewers. Discard any remaining marinade. Broil or grill for about 8 minutes total, turning as they brown, until they are cooked as you like them.