Slice each piece of bread into 3–4 even sticks, about 1 inch wide.
In a shallow bowl, whisk together the eggs, milk, sugar, cinnamon, vanilla, and salt.
Dip each bread stick in the custard, coating all sides, and let excess drip off.
Heat butter in a nonstick skillet over medium heat. Cook the sticks in batches for 2–3 minutes per side until golden and cooked through.
Optional oven method: Bake at 425°F for 12–15 minutes, flipping halfway.
Optional air fryer method: Air fry at 375°F for 8–10 minutes, flipping halfway.
Serve warm with maple syrup.