Remember when I mentioned my pink plastic tumbler awhile back? And how I only put water in it to prevent that gross mildew-y taste? Well, unfortunately, it still developed that taste!
But I have the easiest solution ever- put about a teaspoon of baking soda in the cup, fill with hot water, and let sit for about 20 minutes. Rinse out and you’re good to go!
I’ve heard distilled vinegar is also great for cleaning plastic tumblers. You can also combine it with water and run it through your coffeemaker to clean it periodically.