Preheat your oven to 350°F (175°C).
Lightly grease a muffin tin or line it with cupcake liners.
In a mixing bowl, combine the egg yolk, almond milk, 1/4 cup fat-free Greek yogurt, and vanilla extract. Whisk until well blended.
In a separate bowl, mix together the old-fashioned oatmeal, baking powder, cinnamon, and sweetener. Stir to combine.
Gradually add the dry mixture to the wet mixture, stirring until just combined.
Gently fold in the sprinkles.
Spoon the batter into the prepared muffin tin, filling each cup about three-quarters full.
Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
Let the cupcakes cool in the tin for a few minutes before transferring them to a wire rack.
