Reusable water bottles have become widespread in many countries as more people try to avoid single-use plastics. A recent study found that even when filled with clean water, bottles can still have bacteria inside if not washed properly. Researchers discovered that germs can multiply quickly within a single day, especially when bottles are refilled many times. The problem happens because the inside of bottles is often moist and comes into contact with the mouth and hands. Health experts said that cleaning is essential to stop microbes from spreading and to keep daily drinking habits safe and sustainable.

Experts explained that washing bottles regularly is a simple but effective way to prevent health problems. Warm, soapy water and a bottle brush can help remove germs from tight areas like lids or straws. For deeper cleaning, some bottles can be washed in the dishwasher or with baking soda and vinegar. Glass bottles are easier to clean, while plastic and metal ones may keep germs in small scratches. Keeping a consistent cleaning routine supports both hygiene and environmental protection, showing that small actions can make a big difference in healthy and eco-friendly living.