There could be a few reasons your cupcakes aren’t coming out clean. If your batter is high in sugar, the heat can caramelize the sugar content and cause it to stick. If you’ve overfilled your cups, the batter can get between the paper and the pan. The number one way to prevent sticking is to avoid overfilling liners. Consumers can also use non-stick liners or lightly grease the liners with cooking spray or butter.