Cover steak in plastic wrap and place in freezer for 1 hour or until hard. Remove from freezer and uncover. Slice steak diagonally across the grain into 1/16 inch thick slices.
Mix steak, sugar, soy sauce, mirin, ginger, sesame oil, and garlic in a large re-sealable plastic bag. Seal and shake slightly to make sure all steak is covered. Place in refrigerator and marinade for 1 hour, flipping bag a few times.
Turn on grill.
Take steak out of bag, lie in a grilling basket coated with cooking spray and place on grill. Cook for 2 to 3 minutes on each side or preferred level of doneness.