In a large saucepan, cook apples and water over medium heat for 10 minutes or until apples are tender. Combine 1/2 cup sugar, cornstarch, cinnamon and nutmeg; stir into apple mixture. Bring to a boil; cook and stir for 2 minutes or until thickened. Remove from the heat; stir in lemon juice.
Spread six slices of bread with 1/3 cup filling; top with remaining bread. In a shallow bowl, beat the eggs, milk, vanilla and remaining sugar.
Dip sandwiches in egg mixture. Cook on a lightly greased hot griddle until golden brown on both sides. Sprinkle with confectioners' sugar if desired.