But that's not all the lid has to offer. Use one hand to push the button, and it flips open to reveal a two-in-one spout. We love that you can sip from the straw or use the wider opening to grab a big gulp of cold water without needing multiple lids. The 64-ounce Iron Flask Water Bottle is our favorite large capacity option if you want to space out your refills. (However, we also stand by the other five sizes if you're in the market for something smaller.) We love that it comes with three different caps: a straw lid with a carrying loop, a flip lid, and a stainless steel cap that covers the bottle's wide mouth opening. Drinking enough water has plenty of benefits: “Staying hydrated is key for not only your body’s performance, but also mental clarity and productivity," explains Krista Todini, RDN, a registered dietitian nutritionist. Although the exact amount you should be drinking varies, it's safe to say that adding another glass or two to your daily routine is a good idea for most people.

to 5 stars: These are the best stainless steel water bottles we tested. We recommend them without reservation.For a stainless steel water bottle that comes with a filter built in, we love this option from Brita. It filters out unpleasant tastes and odors, for fresh-tasting water with every sip. We like that the filter is included at a similar price to most other bottles on our list (although you'll need to replace it regularly to reap the full benefits, according to the brand). Most bottles on our list have double-walled insulation to keep your beverage hot or cold (more on how this works later). But Corkcicle's Canteen has triple-walled insulation, for even better results. This bottle excelled in our temperature tests, lowering the temperature of our ice-filled water by 5 degrees after six hours.

This lightweight bottle features a sleek, stylish design that comes in almost 40 colors and patterns, from solid hues to botanical prints. We love that it's leakproof, with a secure, screw-on lid. Available in three sizes (9 ounces, 17 ounces, and 25 ounces), the narrow silhouette makes this bottle easy to carry with you, sliding in most bags and cupholders with ease.

The verdict: Reusable water bottles

We liked that Hydro Flask's 24 oz Lightweight Trail Series Water Bottle has a convenient handle and a sleek silhouette that fits in most cupholders. However, when we dropped it, the lid almost flew off, and the slippery, shiny finish was tough to hold. Single-walled insulation means the bottle is made from a single layer of stainless steel. You won't find any single-walled bottles on our list because they don't stabilize temperature very well, meaning your water won't stay cold over time.