In a pie plate or similar dish, whisk together eggs, milk, sugar, and vanilla extract. Using your hands, dip each assembled french toast stick into the egg mixture, turning to coat all sides well. Allow excess egg mixture to drip off of french toast stick and then transfer it to the prepared baking sheet. Lightly coat the top of the french toast sticks with non-stick cooking spray. Bake for 8 minutes then remove the baking sheet from the oven and use a spatula to flip each stick over. Return to oven for an additional 7 or 8 minutes or until well toasted on both sides. Remove from oven. Sprinkle with powdered sugar, if desired, and serve with maple syrup for dipping.