In small bowl, beat egg and water to form egg wash. Brush top of each biscuit with egg wash; coat top with French-fried onions. Bake as directed on can. Cool. Split biscuits; set aside.
In 10-inch skillet, cook bacon over medium heat until crisp. Drain on paper towels.
In same skillet, brown meatballs until golden. With back of spoon, gently press down on meatballs to form a burger shape. Remove from heat. Top each with slice of cheese; let stand until melted.
To assemble each slider, top bottom half of biscuit with burger, bacon and 1 tablespoon mayonnaise; cover with top half of biscuit.