Cups with a plastic top and straw may prevent messy drink spills; however, the straw interior often becomes clogged with mold, especially in hot weather. Replacing your straw with a disposable one may be a bad idea if the hole in your cup's top is unusually sized. Permanent straws made out of glass can shatter if they are dropped, and metal straws may give your drinks an unpleasant aftertaste. It is fairly easy to get mold out of the plastic straw that comes with your cup using pipe cleaners that you can buy at any crafts or tobacconist store.
Fill your kitchen sink halfway with hot soapy water, and place the moldy straw into the water. Lay a heavy dish on top of the straw if necessary to keep it submerged. Let the straw soak in the soapy water for about 10 minutes to loosen the mold.
Remove the dish and straw from the soapy water. Run clear warm water from the faucet into the straw to push out any larger pieces of mold. Drain the kitchen sink of the soapy water.
Wet a pipe cleaner made out of chenille or terry cloth with warm water. Ensure that the pipe cleaner is as straight as possible, then push it through the straw in and out several times to remove any mold that remains within. Use a larger pipe cleaner or one wrapped in a non-pilling cotton cloth if the first pipe cleaner is too small to clean the straw effectively.
Rinse the straw, pipe cleaner and cloth repeatedly under the sink faucet with warm water, and continue to push the pipe cleaner through the straw until there is no mold remaining inside.