Whisk the eggs, milk, cinnamon, and vanilla together in a big, shallow bowl.
Place slices of bread, one or two at a time, in the egg mixture and let it soak for 2 minutes. Flip and soak for another 1 minute (both bread sides should be fully covered in the mixture).
Meanwhile, melt butter at medium-low in a broad skillet. Place bread slices in a skillet until melted and cook until golden brown, 1 to 3 minutes on each side;
Repeat for the butter and bread remaining.
Serve directly, topped with berries and if desired, syrup or honey.
Serve directly, topped with berries and if desired, syrup or honey.