Rinse strawberries. Cut off leafy tops. Slice ⅛-inch thick.
In a small bowl, whisk cocoa powder and sugar together with a fork. Set aside.
In a second small bowl, beat egg with a fork until well blended.
Add milk and cinnamon to egg. Beat about 1 minute more.
Coat medium skillet with non-stick cooking spray. Heat over medium heat.
Dip one piece of bread in egg mixture. Flip to coat both sides. Remove from egg mixture, shaking off any excess egg coating. Place quickly in hot skillet. Cook until golden brown, about 2–3 minutes per side. Remove from pan.
Repeat steps 5 and 6 until each piece of bread has been cooked.
Top each piece of bread with 3 Tablespoons sliced strawberries. Dust generously with cocoa mixture.