Make the batter for the French toast by whisking together the eggs, milk, vanilla, and cinnamon until evenly blended. Cover and refrigerate.
Pay close attention while you make the caramel apples - put the sugar in a large dry skillet and place it over medium-low heat. Stir constantly with a wooden spoon until the sugar melts and begins to caramelize, about 5 minutes. Be careful; the sugar is really hot at this point. Still stirring, add the butter, which will foam a little. Once the sugar and butter become a caramel sauce, fold in the apple wedges. Now, because the apples are cooler than the sugar, the sugar may start to seize and harden, but don't freak out -- keep stirring, once the apples warm up the caramel will smooth out again. When the caramel sauce starts to form around the apples, pour in the maple syrup. Give it a stir and simmer for about 10 minutes until the apples are fork tender. Pull them off the heat and keep warm until you are ready to serve.
For the French toast itself, warm the butter in a large non-stick skillet over medium-low heat. You probably will only be able to fit a couple of croissants in the pan at once, so prepare these in batches. Take a croissant half and quickly dredge it in the batter. The key word here is quickly; the croissants are very soft and will disintegrate if soaked in the batter. Lay the croissants in the pan, cut-side down, and cook for 4 to 5 minutes. Carefully flip them over with a spatula and brown the other side.
The presentation is like a caramel apple sandwich - take the bottom half of the croissant and put it on a plate, spoon some of the caramel apples on top of that, and cover with the top 1/2 of the croissant. Dust with confectioners' sugar and cinnamon and serve.