Preheat your air fryer to 325°F (163°C) and lightly spray the basket or place down an air fryer liner sheet.
In a medium mixing bowl, whisk together the zero sugar cake mix and 1 cup of high-protein flour until fully combined with no large lumps.
Pour in the sugar-free syrup and 1/3 cup of milk. Stir well with a spatula until a firm dough forms, adding extra milk 1 tablespoon at a time only if the mixture remains too dry to roll.
Gently fold the rainbow sprinkles directly into the dough mix using your spatula, being careful not to overmix and bleed the colors.
Divide the final dough mixture into 16 evenly-sized portions using a scale, and roll each piece tightly between your palms into a clean ball shape.
Place the bites inside the preheated air fryer basket, leaving space between them, and cook at 325°F (163°C) for 10 minutes until set.
Let the cooked bites sit and cool for 3 minutes on a plate to firm up their interior texture.
Optional: Roll each warm bite inside a quick powdered sweetener and milk glaze if desired.
