You might recall a scene from a World Tour race, where a pro rider finishes their bottle and tosses it into the roadside ditch. When it comes to hygiene, that may be the smartest move they could make. Life inside a bottle is, to put it mildly, a microbial jungle—and not the Disney kind. If we could blow it up to scale, you’d see a steamy, tangled mess of things you do not want to drink.
Ever reached into your bottle and felt that slimy coating on the inside? Hate to break it to you, but that’s not just leftover drink. That’s a bacterial biofilm.
A cycling water bottle is far from a sterile environment. Even water straight from the tap—no matter how clean or well-regulated—contains bacteria. Standards vary by country, of course, but even high-quality water isn’t 100% bacteria-free. And under normal circumstances, that’s not a problem, as most bacteria aren’t harmful.
The trouble starts the moment the bottle meets its rider.
If you dive into any of the studies on “what happens inside reusable bottles,” you’ll quickly discover that this is where the horror show begins. Every time you take a sip, bacteria from your lips make the jump into the bottle, where they get to work multiplying. Fast.
One study published in the Journal of Food Protection found that more than 20% of reusable bottles contained coliform bacteria or faecal matter. That gunk gets in there from—you guessed it—your mouth, often also via hands that weren’t washed quite well enough. These bacteria can cause anything from mild stomach issues to full-on digestive misery. And while they can grow even in cooler temperatures, they thrive in heat; say, when you leave your bottle out in the sun. In just one day, bacterial colonies can explode into the millions.
And that’s just water. Add any other type of drink into the mix, and things get worse.
What fuels you also fuels bacteria. Sugary drinks in particular act like a superfood for microbial life. One study found that anything other than plain water creates an ideal environment for bacteria and mould, with protein shakes being a special kind of nightmare. And don’t even think about sharing your bottle. Your immune system is familiar with your own bacteria, but someone else’s? Not so much. Most people have between 500 and 600 different types of bacteria in their mouths. What’s harmless for one person might mess up someone else completely. You could be carrying an infection without even knowing it, thanks to your well-trained immune system keeping things under control.
If this is starting to feel like one of those articles you wish you hadn’t read, you’re not alone.
Carl Behnke, a food safety expert from Purdue University in Indiana, ran an on-campus experiment where he stopped random students and faculty to inspect the condition of their reusable water bottles. “One thing that really stood out was how many people didn’t want to know the results,” Behnke told the BBC. Why? Because deep down, they already knew their hygiene habits were questionable at best. In fact, 15% of participants admitted they never clean their bottles.
Behnke and his team recommend using a dishwasher with a sanitising cycle as the most effective cleaning method. (Assuming your bottle is dishwasher safe, of course.)
So congratulations to all who’ve made it this far without running to the sink with a bottle brush in hand and a bottle of bleach. That’s some serious mental stamina.
Now, what about the material of your bottle? Studies show that metal bottles are slightly more resistant to bacteria buildup than plastic ones. Glass bottles came out on top: they’re non-porous, easy to clean, and their transparency means you can see when they need a good wash.
Still, material matters less than shape. Bottles with narrow necks are harder to clean than wide-mouthed ones. And let’s not forget the lids and valves, those are microbial hotspots too. Across the board, the science agrees: thorough, regular cleaning reduces bacterial risk. Neglecting your bottle invites a germ party.
So if you’re now nervously glancing toward your kitchen sink, here are some quick bottle-care tips to keep your bidon in fighting shape:
- Stick to water. Sugar-filled drinks or powdered mixes = bacterial bonanza.
- Empty and rinse the bottle after every ride.
- Scrub it with soap and a brush at least once a week.
- Pay attention to the drinking valve—it needs love, too.
- Let the bottle air-dry upside down. Never store it while wet.
- Don’t share it with anyone. Not even your ride buddy.
- If your bottle starts to smell funky, toss it. Don’t hesitate. Just replace it.
Stay hydrated. Stay clean. And may your bidon never turn into a horror jungle.
