In a large bowl, beat eggs, milk, sugar, vanilla, salt, and cinnamon with a whisk until smooth. Set aside.
Add Cinnamon Toast Crunch to a large zipper storage bag. Remove the air from the bag and seal it shut. Use a rolling pin (or your hands) to slightly crush the cereal into a smaller crumb. (You will end up with about 4½ cups crushed cereal.)
Add the crushed cereal to a plate in an even layer.
Heat griddle over medium heat, about 350°F. Add a tablespoon of butter to the griddle.
Working in batches, dip slices of bread into the egg mixture (not soaking the bread) and then into the Cinnamon Toast Crunch crumbs. Press down slightly so the crumb sticks.
Place the bread on the hot griddle and cook for 1 to 2 minutes on each side, or until golden brown. Add more butter before cooking the next batch.
Serve with room temperature butter, maple syrup, whipped topping, or more cereal. Best served hot.