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. Purist's Mover Vacuum Water Bottle has a stylish, compact design. But for how expensive it is, we wish it could go in the dishwasher. The cap is also hard to open and leaked when we dropped the bottle from waist height.

Lainey Younkin, MS, RD, LDN, is a registered dietitian always looking for ways to help her clients drink more water. She has personally owned many stainless steel water bottles because she can’t stand lukewarm water and loves any bottle that keeps her H20 ice cold for hours. Made from 18/8 pro-grade stainless steel, this Hydro Flask is BPA-free. But while it kept our water cold for three hours, we noticed the temperature had increased by 8 degrees after six hours—meaning this bottle's double-walled insulation isn't effective as others we tested. If insulation is important to you, we recommend investing in Takeya's Actives Water Bottle or Thermoflask's Water Bottle instead. While Takeya's Actives bottle ultimately won out, we also highly recommend this option from Thermoflask. We love that, for a similar price, this bottle comes with two lids—one with a spout and one with a straw—so you can choose your preferred method of sipping. Like Corkcicle's Canteen, S'well's Water Bottle features triple-walled insulation—perfect for keeping your tea or coffee hot all morning long. The brand claims the largest bottle can keep drinks cold for up to 48 hours and hot for around 18. While we didn't test the full extent of this range, the bottle did perform well in our temperature tests, keeping our water fresh and cold after three and six hours.

How much plastic is saved by using a reusable water bottle?

We love the sleek design, which has a modern, angular shape and comes in a variety of bright colors and patterns. The 16-ounce capacity is solid for everyday sipping, and the low-profile lid is completely leakproof, for added peace of mind. to 5 stars: These are the best stainless steel water bottles we tested. We recommend them without reservation. Triple-walled insulation works the same way, except there's a third layer of steel or copper (creating two vacuum layers). S'well's Stainless Steel Water Bottle uses triple-walled insulation to keep drinks cold for 36 hours and hot for 18 hours. The double-walled insulation kept our water icy cold. Thermoflask notes that the bottle will chill drinks for 24 hours or keep them hot for 12, making it a solid choice for your morning coffee or tea. The attached handle is easy to hold, although we wish it could be folded down when not in use.

Next, we select a set bottles to test for ourselves. To see how effective each bottle's insulation was, we fill them with ice and cold water. We use a liquid thermometer to measure the temperature of the water immediately after we pour it, 3 hours later, and 6 hours later, as the bottles sit on a sunny windowsill. However, it did not pass our drop tests, denting and leaking after it hit the floor. Even so, we still recommend this bottle as a convenient, mid-sized option with an effective filter. The bottle's slim design is easy to hold and fits in most cupholders. This, combined with the handy carrying loop that's attached to the lid, enables us to bring this bottle almost anywhere.In testing, we found that this bottle didn't keep our water as cold over time as Takeya's Actives or Thermoflask's bottles did. But with only a few degrees difference, we still think it's a solid option. We're also fans of the lid, which has a unique design that's a delight to drink from.

We also love that the Rambler is dishwasher-safe, for easy cleaning. Choose from over 20 bright and metallic colors to find your favorite style. Water bottles can range in size from 12 ounces all the way up to 84 ounces (or even more). "When choosing a stainless steel bottle, consider what you’ll be using it for," Todini says. "If you’re active in sports choose a lightweight and slim bottle that can easily be carried, or if it’s your everyday water bottle choose one that fits in your bag or car’s cup holder." We love that this sturdy bottle doesn't leak, even when dropped or flipped upside down. But unlike Takeya's Actives bottle, it did dent after multiple falls. Available in a range of jewel tones and sizes, you can grab a smaller bottle for sitting in your car's cupholders or a larger size to cut down on your refill trips. Just note that the larger sizes can start to feel heavy, weighing between 1 and 2 pounds each.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. The wide mouth opening allows us to add ice cubes, while the spout lid ensures we can sip without soaking our shirts. Combined with the handy carrying loop, we recommend this bottle as your everyday go-to, especially if you work out often and need a basic bottle for the gym. To help you stay hydrated, especially during busy days, we recommend investing in a functional water bottle that you can bring with you to the gym and the office. Stainless steel water bottles keep your water cold for hours, are better for the environment than plastic, and aren’t prone to breaking like glass water bottles can be.