In a large bowl beat together eggs, milk, sugar, vanilla and cinnamon. In an ungreased 2-quart square baking dish toss together bread cubes (fruit if added); pour egg mixture evenly over bread mixture pressing lightly with back of a large spoon. This is necessary so the top gets soaked with the wet mixture.
Bake, uncovered, in a 350 degree oven for 40 to 45 minutes or until puffed and a knife inserted near the center comes out clean. Cool slightly. If desired, serve warm with whipped cream or your favorite sauce.
To dry bread cubes, place them in a large, shallow baking pan and bake in a 350 degree oven about 10 minutes, stirring twice.