Heat oven to 375°F. Spray 8 regular-size muffin cups with cooking spray.
In a 10-inch nonstick skillet, cook the ground beef and onions over medium-high heat 5 to 7 minutes, stirring frequently, until no longer pink; drain. Add sloppy joe sauce; cook until heated through. Remove from heat; cool slightly.
1 pound lean ground beef, 1 cup Sloppy Joe sauce, from a 15-ounce can), ¼ cup chopped onion
On a large cutting board, unroll the crescent rolls and press the seams together. Cut into 8 squares with a sharp knife or pizza cutter. Line each muffin cup by pressing 1 dough square in the bottom and up the side of the muffin cup. Divide the sloppy joe mixture evenly into each cup, about 1/4 cup each. Top each evenly with shredded Cheddar cheese, about 2 tablespoons each.
1 can refrigerated crescent rolls (8 ounces), 1 cup Cheddar cheese, shredded
Bake 14 to 18 minutes or until dough is deep golden brown and filling is heated through. Cool in pan 5 minutes; using metal spatula, run around edge of each muffin cup to remove from pan.
Place the crescent cups on a platter for serving. Serve warm.