Treadmill Reviews tested an athlete’s refilled water bottles after a week of use and they found that one contained over 900,000 colony forming units (CFU i.e. a lot of germs) per square centimetre. That’s more than the average toilet seat.
And while that’s a disgusting example, the average person’s water bottle was found to have 313,499 CFU per square centimetre.
Even worse, the researchers found that 60% of the germs they noticed on the water bottles were able to make people sick.
Further research in Practical Gastroenterology explained that manufacturers do not recommend reusing disposable bottles because, "Everyday wear and tear from repeated washings and reuse can lead to the physical breakdown of the plastic, such as visible thinning or cracks. Bacteria can harbour in the cracks, posing a health risk."
So if you’re not feeling too crash hot it might be time to swap out what you’re sucking on.