Traveling with a reusable water bottle is a great way to reduce your environmental impact (and save you from having to spend $5 at the airport just to stay hydrated). But there is a downside: Carrying around an empty bottle in your already tightly packed travel bag is different kind of wasteful.

Thankfully, collapsible water bottles have recently grown in popularity. They're generally made with lightweight, flexible materials like silicone that allow you to fold, flatten, or twist them down to become compact enough to fit easily into your bag (or even your pocket in some cases) and then expand again when it’s time to fill up.

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