In a large mixing bowl, pour in the sugar-free gelatin powder and slowly add the boiling water while whisking continuously. Keep whisking for about 1–2 minutes until the gelatin is fully dissolved and no tiny crystals or granules remain at the bottom of the bowl. This step is important because undissolved gelatin can create a grainy texture later instead of a smooth, creamy fluff.

Set the gelatin mixture aside and allow it to cool for about 10–15 minutes. You want the mixture to still be liquid but no longer steaming hot. If the gelatin is too hot when the yogurt is added, it can cause the yogurt to separate or become curdled instead of silky smooth. Stir the mixture occasionally while it cools to prevent a skin from forming on top.

Add the Greek yogurt directly into the cooled gelatin mixture and whisk thoroughly until everything is fully combined. Continue whisking until the mixture becomes smooth, creamy, and evenly colored with no yogurt streaks remaining. Thick Greek yogurt works best here because it creates a richer texture and boosts the protein content significantly.

Using a silicone spatula, gently fold in the zero sugar whipped topping. Avoid aggressively stirring because folding helps keep the mixture airy and fluffy. Slowly lift and turn the mixture from the bottom of the bowl until the whipped topping is completely incorporated and the texture becomes light, creamy, and mousse-like.

Spoon the finished mixture into serving bowls, glass dessert cups, mason jars, or airtight meal-prep containers. Smoothing the tops slightly with the back of a spoon gives the dessert a clean, bakery-style appearance once chilled.

Place the containers into the refrigerator and chill for at least 3–4 hours, though overnight chilling will give the fluff the best thick, creamy texture. As it chills, the gelatin will lightly set while the yogurt and whipped topping stay soft and velvety.

Serve the fluff cold straight from the refrigerator for the best flavor and texture. Top with extra zero sugar whipped topping, fresh strawberries, raspberries, blueberries, crushed nuts, or even a sprinkle of sugar-free graham cracker crumbs if desired for extra texture and flavor.