The One Nasty Part of Your Stanley Tumbler That Can Get You Sick

shot of water being poured into the stanley cup
Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup

Shoppers just can’t seem to get enough of the Stanley Quencher Tumbler. The 40-ounce reusable steel cup is insulated, keeping your drink of choice cold for hours, and has become somewhat of a statement piece with its abundance of colors, designs, and limited-edition drops. Some brands are even trying to mimic the tumbler’s success by crafting their own dupes of the viral product. While I can’t try to explain the trend, I’m here for an environmentally-friendly product that encourages people to drink more water!

But as with all reusable water bottles, it’s crucial to keep them clean — which is apparently harder than it sounds. Some TikTok creators (like @skysayingthings and @jenn_rupp) have taken to the app to share videos of the mold and mildew that has been collecting and hiding in their tumbler, despite cleaning out the bottle frequently. There was even a viral story of a young girl who caught a months-long “mystery illness” from mold growing in a similar-style water bottle. So, what gives? And why do these water bottles get so nasty?

I spoke with Becky Rapinchuk, cleaning expert, author, and founder of Clean Mama, and Melissa Maker, cleaning expert and founder of Clean My Space, to learn the best way to clean the cup, how often, and which household items will serve you best when cleaning. 

“The best way to clean a Stanley is to clean it after each use,” explains Rapinchuk. “Make sure it’s not sitting under a car seat, in a bag, or backpack. If you’re washing it after each use, it’s not as likely to grow mildew.” The cleaning pros recommend following these steps when cleaning out your Stanley tumbler to avoid any bacteria build-up or chance of illness:

How to Clean a Stanley Tumbler

shot of the inside of a stanely tumbler.
Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup

1. Remove the lid and straw and empty the tumbler.

shot of soap being poured into the stanley cup
Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup

2. Add a drop of dish soap to the Stanley and fill it up halfway with hot water. If the tumbler is stinky, add 1/4 cup white vinegar. (Maker also suggests sprinkling some baking soda into the tumbler if there are any stains on the interior.)

shot of a light blue stanley being held
Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup

3. Close the cup and shake the soap and water mixture, and scrub the exterior with a brush. You can also use a bottle brush to scrub both the interior and exterior of the container. (Rapinchuk suggests using a non-abrasive cleaner for the exterior as Stanleys are composed of stainless steel.)

shot of the stanley straw being cleaned.
Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup

4. Scrub the inside of the straw with a straw brush and run the straw under hot water until it runs without bubbles.

shot of mouthpiece being taken apart
Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup

5. Take the lid apart by squeezing the fastener from the inside of the lid.

shot of the mouthpiece being pulled apart.
Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup

6. Take the lid attachment and push the silicone knob in the center, or either of the sides. Peel the silicone piece off completely. (This doesn’t need to be taken off and cleaned every single time, but it “helps to remove buildup and mildew,” according to Maker.)

shot of the mouthpiece being scrubbed by a toothbrush
Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup

7. Scrub all three lid components with dish soap, hot water, and a toothbrush to get in every nook and cranny. (While the body of the tumbler technically isn’t dishwasher-safe as it may damage the colorful coating, you can throw the three lid elements in the dishwasher for a more thorough cleaning.)

shot of the stanley on a drying rack
Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup Credit: Photo: Alex Lepe ; Prop Stylist: Tom Hoerup

8. Rinse all components thoroughly before air drying. Finally, put it all back together.

If you follow all of these steps every time you clean your Stanley tumbler (which should be at least once a week), odds are good you’ll avoid mildew, black mold, and any illness associated with what’s growing inside the lid components. You can’t beat the pure convenience of having a tumbler as exceptional as a Stanley, but while it’s important to stay hydrated, it’s just as crucial to keep your cup clean — for your own safety.