Cut the crusts off each slice of bread and flatten using a rolling pin.
Add 1–2 teaspoons of your chosen filling about 1 inch from one edge. Roll the bread tightly into a log shape.
In a shallow bowl, whisk eggs and milk until smooth.
In another bowl, mix sugar and cinnamon.
Heat a skillet over medium heat and melt butter.
Dip each roll into the egg mixture, coating evenly. Place seam-side down in the pan.
Cook French Toast Roll-Ups until golden brown on all sides, about 2 minutes per side.
Immediately roll the warm pieces in cinnamon sugar until fully coated.
Serve warm, optionally with syrup or fresh fruit.