Clothes stick together in the dryer due to static electricity. Different fabrics exchange electrons as they rub against each other in the dryer. Some clothes become positively charged and others become negatively charged. These opposite static charges cause the clothes to stick together and produce crackling sparks when pulled apart.
Antistatic dryer sheets prevent clothes from sticking together in the dryer. They contain positively charged compounds that coat and lubricate the clothes as they tumble around in the hot dryer. Positive charges from the dryer sheets neutralize negatively charged fabrics, preventing the exchange of electrons that causes static cling. Fabric softeners function on the same principle.