Preheat grill to medium-high heat and lightly oil the grate.

Break up ground beef with the tip of a fork in a bowl. Drizzle in the soy sauce, sake, mirin, Worcestershire sauce, and sriracha sauce; crumble in brown sugar. Use tines of a fork to evenly distribute ingredients. Finish mixing with your hands (ideally your hands should be very cold for this). Shape into 4 equal-sized patties.

Grill until browned and cooked through turning once, 3 or 4 minutes per side. When burgers develop a slight dome shape and juices begin to come through the top surface, they are done. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).

Serve burgers on slider buns with lettuce and tomato slices.