In a shallow wide bowl, whisk together the liquid egg whites, vanilla protein powder, ground cinnamon, vanilla extract, and sweetener until the protein powder is fully integrated and no large lumps remain.

Preheat a non-stick skillet or griddle over medium heat and lightly coat with non-stick cooking spray.

Submerge one slice of bread at a time into the egg white mixture, allowing it to soak for approximately 10 to 15 seconds per side to absorb the liquid without becoming structurally unstable.

Place the soaked bread slices onto the preheated skillet.

Cook for 3 to 4 minutes on the first side, or until the egg coating is set and golden brown.

Flip the slices and cook for an additional 3 minutes on the second side.

Remove from heat and serve immediately with optional high-protein toppings such as Greek yogurt or sugar-free syrup.