You may be using plastic lids on cups the wrong way
You may be impressed to know there is a subtle design and purpose behind the plastic lid on your cup. Although this is a kind of hidden design feature, it is not the only product that has a secondary benefit. Plastic lids are useful for keeping your drink from spilling, but they also have another utility that few people are aware of.
You will surely notice that the plastic lid has three bumps, and the bottom of your cup will easily fit on the ridge. Moreover, when you are sitting down and enjoying a hot beverage, it can help prevent spills. However, this hack applies to all plastic cups, not just the ones we know from Starbucks. And there you have your drink coaster.