What's not to like about reusable water bottles? They're better for the environment and your wallet, and they help you stay hydrated, so you can feel and perform your best. But over time they can get a little gross. So, just how often should you swap your bottle out? It really depends.

"Plastic water bottles can start to break down after continued use and need to be replaced about once a year," Leanne Stapf, chief operating officer at The Cleaning Authority [1], told POPSUGAR. "Glass bottles [2] have a long shelf life, but can break easily, so they aren't ideal for those with an active lifestyle. Stainless steel bottles are sturdy and rust and stain resistant, and generally only need to be replaced due to normal wear and tear."

Cedrina Calder [3], MD, a preventive medicine doctor in Nashville, TN, explained that there are a few warning signs that it's time to replace a bottle, regardless of which type you own. "You should replace your bottle when the bottle has an odour that you can't get rid of despite thorough cleaning and trying various cleaning methods," Dr. Calder said. "Also, when the lid or mouthpiece has gunk or buildup that you aren't able to get to and remove with proper cleaning, or the plastic on the bottle has started to crack — this increases the chances that bacteria can collect within the cracks and grow."

To keep germs at bay, you should clean and disinfect your bottle after every use [4]. (Yes, even if that means daily.) "Many people go weeks without washing their water bottles because they don't look dirty, but looks can be deceiving," Leanne said. "Bacteria grows in dark, moist environments, which makes the inside of a bottle the perfect breeding ground for bacteria."

To eliminate any foul odours and bacteria [5], Leanne suggests mixing a solution that is 50/50 bicarbonate of soda and water, pouring it into your bottle, and allowing it to soak for 10 minutes. To get an even deeper clean, you can purchase an inexpensive bottle brush to scrub the inside [6]. Another popular way of cleaning a reusable bottle is done by using a mixture of ¼ cup white vinegar and ¼ cup water as a disinfectant. All you have to do is let the solution soak in the bottle overnight and scrub away any remaining film or scum in the morning.

"Make sure to also look at the bottom of your bottle before cleaning," Leanne added. "Many reusable water bottles are dishwasher safe, which makes cleaning fast and simple!"