In a blender, combine vanilla protein powder, almond milk, cinnamon, vanilla extract, and sugar-free syrup.
Blend until smooth and well combined.
Pour the mixture into the Ninja Creami container and freeze for 24 hours.
Once frozen, process the mixture in the Ninja Creami machine as per the manufacturer’s instructions.
Serve immediately and top with crushed Cinnamon Toast Crunch cereal if desired.