In a blender, combine the milk, vanilla protein powder, sugar-free vanilla pudding mix, stevia, vanilla extract, and a pinch of salt. Blend until everything is fully combined and smooth.
Pour the blended mixture into your Ninja Creami pint, secure the lid and place the pint in the freezer for at least 24 hours.
After 24 hours, take the pint out of the freezer and run it under hot water on all sides for 1–2 minutes.
Spin it on Light Ice Cream mode.
Respin it 1–2 times until it reaches your desired consistency.
Once your ice cream is done, pour in 1 cup of diet or zero-sugar root beer. You can gently mix it in for a swirl effect or pour it over the top for a true float experience.
Top your float with sugar-free whipped cream and a cherry (optional) and enjoy!