Combine egg and water; set aside. Combine Parmesan cheese and bread crumbs; set aside.
Place each piece of pork between two sheets of heavy-duty plastic wrap; flatten to 1/4-inch thickness using a meat mallet or rolling pin.
Dip pork in egg mixture and dredge in crumb mixture. Cook pork slices in hot oil in a large skillet over medium heat just until browned, turning once. Arrange pork in a lightly greased 8-inch-square baking dish; top with spaghetti sauce.