Whether they're made from plastic or glass, stacked drinking glasses occasionally become stuck together. Don't break the glasses or risk cutting your hands trying to twist them apart. Instead, try a simple remedy that easily separates the stuck stack. A basic heat principle works to release stuck cups, nested bowls or any stackable open containers.
Heat water to almost to boiling. Pour the hot water into a heatproof bowl or pan that's deep enough to submerge the bottom glass of the stack. A sink works if you don't have a container large enough.
Lower the stack into the hot water until the bottom glass is submerged. Hold the stack vertically so only the bottom glass is in the hot water. The heat causes the bottom glass to expand slightly.
Fill the top glass with cold water, adding ice cubes to cool it quickly. The cold water causes the top glass to contract slightly.
Wait 30 seconds and gently pull the glasses apart. If they don't come apart easily, return them to the hot and cold water. It may take several minutes to unstick the glasses.
Place the stack upright on a flat table or counter.
Drip a few drops of light oil, such as sewing machine oil, olive oil, even smutch petroleum jelly, around the lip of the lower glass. Allow the oil or jelly to seep between the glasses for a few minutes.
Jiggle the top glass gently to loosen it, then pull gently to separate the glasses. If the glasses don't separate easily, drizzle more oil or place more jelly around the joint and allow more time.