Preheat your oven to 350°F and spray an 9x13 casserole dish lightly with nonstick spray.
Slice the slider buns in half (keep them connected). Place bottom buns, cut side up in your casserole dish. Lightly brush with extra melted butter.
Bake bottom slider buns for 5 minutes, until they are light golden brown. Set aside.
In a heavy-bottom non-stick skillet, combine the ground beef with the onion and garlic. Brown the beef on medium-high heat by breaking it up and flipping as it browns. Once cooked, drain any excess grease and stir in the sloppy joe sauce.
Layer your ingredients over the bottom buns, starting with the slices of Colby-Jack cheese. Add ground beef with sloppy joe sauce and another layer of cheese, if desired, and finally place the bun tops on last.
Brush the tops of the buns with melted butter using a small bowl and pastry brush.
Bake in your preheated oven, uncovered, for 15-20 minutes or the tops are toasted, cheese is melted and the sliders are heated throughout. Brush bun tops with remaining butter and sprinkle with sesame seeds after baking.
Slice the sliders and serve!