Many people carry a reusable water bottle as part of a healthy, eco-conscious routine. But those same bottles can become reservoirs for bacteria, yeast and mold if they are not washed and dried properly. The result can be minor stomach upset for most people and, for those who are very young, elderly, or have weakened immune systems, a more serious infection.

Bottles become contaminated through ordinary use: hands and mouths transfer microbes, sugary drinks leave residues that feed growth, and warm, humid interiors encourage biofilms — slimy layers of mixed microbes that cling to surfaces. Insulated bottles with narrow necks and straws present particular cleaning challenges because their shapes make it harder to reach every surface. Caps, seals and straw components are common hiding places for grime and should be taken apart and cleaned as thoroughly as the bottle itself.

For routine care, wash bottles daily with hot water and dish soap, using a bottle brush to scrub the interior. Many models are dishwasher-safe; consult the manufacturer’s instructions and place components on the top rack when appropriate. After washing, allow bottles and lids to air dry completely; moisture left inside encourages microbial regrowth. For a deeper clean, disinfecting once a week is prudent: a diluted bleach solution or a vinegar soak can reduce microbial load, followed by thorough rinsing. Boiling water can sanitize stainless steel bottles that are rated for it, while delicate materials and insulation may require gentler approaches. Replace worn or cracked lids and rubber seals, which are difficult to sanitize effectively and can trap contaminants.

These individual practices have public health consequences. When people get sick from contaminated bottles, that can lead to lost days of work or school and extra strain on caregivers and health services. The risks are not evenly distributed: people without reliable access to clean water, adequate sanitation, or basic cleaning supplies face greater barriers to maintaining safe reusable containers. Students, precarious workers, people experiencing homelessness and families in under-resourced neighborhoods may be less able to wash and dry bottles regularly, amplifying health disparities.

Policy and infrastructure can help close that gap. Employers, schools and public transit hubs can support healthier habits by providing clean drinking-water stations, accessible sinks, and clear guidance about device care. Public health messaging should not only promote reusable bottles for environmental reasons but also include practical cleaning instructions and resources so all communities can benefit without added risk.

Cleaning a water bottle takes a few minutes but can prevent avoidable illness and make reusable containers a safer, more equitable option. Regular maintenance preserves the health of individuals and communities while sustaining the environmental and economic benefits that many people choose bottles for in the first place.