With hundreds of portable reusable water bottles on the market, choosing one depends on what you need it for (a workout, cycling, desk duty), how you sip (via straw, spout, etc.) and whether you like glass, stainless steel or plastic.

Once you’ve chosen a bottle, though, treating it right and keeping it clean is crucial to keeping you healthy — especially during warm humid weather that encourages bacteria growth.

Have you left a sports bottle half filled in a hot car or stashed it in a damp place (read: sweaty gym bag) or forgotten it for days with leftover juice or sports drink dribbled all over the mouthpiece? Bacteria loves that, creating bad smells and bad tastes.

“People have to remind themselves that those bottles are just like their glasses and plates and other dishware at home,” says Dr. Georges Benjamin, who heads the Washington, D.C.-based American Public Health Association. “They need to be cleaned.”

“Once a day, you should take it home and clean it out,” he says, “and hot soapy water will do the job.”

Regularly washing the bottle is important, especially if it’s held something sticky (juice or sports drink) or pulpy.

And while some new bottle designs separate in the middle for easy cleaning, if a bottle doesn’t and “you can’t get your fingers in there,” says Benjamin, “you may need a brush or other utensil to actually clean the places in the corners, particularly in the bottom and around the tops and the insides of the lids.”