Stacking plastic cups within other plastic cups may seem convenient, but this space-saving storage method doesn't necessarily save time. Using your bare hands to force apart two plastic cups that are stuck together can become a time-consuming and frustrating experience. Trapped air and moisture in the spaces between stacked plastic cups create suction, which forces the cups together. Plastic cups become harder to separate the longer they remain stuck together, but you can promptly force apart two stacked plastic cups using basic techniques.
Fill the top plastic cup with ice cubes. Set the stuck-together cups aside for now.
Pour 1 qt. of hot water into a kitchen bowl. Submerge the bottom plastic cup in the hot water, keeping the top cup out of the water. Hold the stuck-together cups in this position for three minutes.
Remove the bottom cup out of the hot water and pour the ice cubes out of the top cup. Dry the wet plastic cup with a towel.
Grasp the top cup with one hand and the bottom cup with the other. Pull the two cups apart, twisting them while you pull.
Repeat the entire procedure if the plastic cups still remain stuck together.