Lightly coat a 9x13 inch baking pan with cooking spray.
Line the bottom of pan with bread cubes.
In a large bowl, beat together eggs, milk, 4 tablespoons sugar, salt and vanilla. Pour egg mixture evenly over the bread.
Dot with butter.
Let stand for 10 minutes.
Combine remaining 4 tablespoons sugar with 1 teaspoon cinnamon and sprinkle over the top. Bake in center of the oven for 45 to 50 minutes, until top is golden.
Modifications
I used a whisk for the egg/milk mixture because it was a good day. Either a hand mixer, blender or food processor would work well as well.