Season steak to taste and grill to rare, remove from heat and cool at room temperature for 20 minutes, then chill. Or start with leftover grilled sirloin steaks.
Slice as thinly as possible, across the grain and on a bias, and then place in a microwave safe bowl, tossing with the BBQ sauce of your choice. Toast buns or rolls on a grill or under a broiler, and heat BBQ sirloin in the microwave in short bursts – resting and stirring between bursts so the meat is not overcooked.
Serve sliced meats on toasted buns. If making cold sandwiches to go, carry bread and BBQ separately, assembling just before eating.
