In a large bowl, whisk together the eggs, milk, vanilla extract, and cinnamon.
Cut the banana bread into 8 slices, approximately 1 inch thick, if it is not already sliced.
Arrange the banana bread in a 9x13-inch baking dish. Pour the egg mixture over the bread and let it soak for 1-2 minutes, turning the slices if needed to coat both sides.
Preheat a griddle to 350°F or heat a large skillet over medium heat. Melt the butter on the griddle or skillet.
Cook the coated banana bread for 2-3 minutes per side, or until golden brown. Work in batches if needed.
Serve warm with syrup and fresh bananas, if desired.
Notes
Refrigerate the leftovers in an airtight container for up to 3 days.