Preheat the oven to 350°F (175°C) and lightly grease a baking dish or sheet pan large enough to hold the slider buns in a single layer.

In a skillet over medium-high heat, cook the ground beef with salt, black pepper, onion powder, and Worcestershire sauce until browned and fully cooked, breaking it into small crumbles as it cooks.

Drain any excess grease from the beef, then stir in the finely diced onion and chopped pickles. Remove from the heat and set aside.

In a small bowl, mix together the mayonnaise, ketchup, yellow mustard, sweet pickle relish, white vinegar, and sugar to make the special sauce.

Place the bottom halves of the slider buns in the prepared baking dish. Spread a thin layer of the special sauce over the buns, then top with the cooked beef mixture.

Lay the American cheese slices over the beef, overlapping if needed, then place the top buns over the cheese.

Brush the tops of the buns with melted butter and sprinkle evenly with sesame seeds.

Bake for 10 to 12 minutes, or until the cheese is melted and the sliders are heated through and the tops are lightly toasted.

Carefully lift the top buns, add shredded iceberg lettuce, and drizzle or spread on more special sauce if desired. Replace the tops and serve warm.