Put the egg, milk, sugar and cinnamon in a bowl and whisk to combine.
Cut the bread into ½-inch pieces. Peel the apple, remove the core and dice into ¼-inch pieces.
Mix the bread with apple and divide between 2 mugs. Pour ½ of the egg mixture into each mug. Mix to combine. Let stand 1 min. Place the mug in the microwave and heat for 3 min on high. Garnish with extra cinnamon. Serve immediately.