In a large bowl, whisk together the eggs, eggnog and vanilla. Pour into a pie plate or shallow dish and slice the bread into 1-inch thick slices.
Preheat your waffle iron and spray it with nonstick spray. Dip two pieces of bread into the egg mixture, letting them sit for a minute and turning to coat both sides. Place one or two (whatever your iron will accommodate) into the waffle iron and gently close the lid. Cook until the steam slows down, or until golden.
Repeat with remaining bread and egg mixture. (French toast can be kept on a wire rack set on a baking sheet in a 250F oven while you cook the rest - the rack will keep them from getting steamy and soggy on the bottom.)
Serve warm, with maple syrup.