Bringing home a bunny requires setting her up with all the necessities for a comfortable and happy rabbit life. One of those essentials is a water bottle to ensure she has access to a supply of water at all times. Rabbits are fond of flipping things over, like dishes full of food or water, so a water bottle that can't be spilled is the best way to provide your bunny with a tamper-proof water supply.
Rabbits come in all sizes and so do their water bottles. Since your rabbit may need to drink up to 1/2 cup of water per pound of body weight every day, choose a bottle that will hold enough water for her to get her through 24 hours. If you have a 6-pound rabbit, a liter-sized water bottle would be a more than sufficient size. Get multiple bottles or one that is larger than a liter if you won't be able to refill your bun's bottle every day.
Once you start shopping for water bottles for your bunny you'll be faced with many design styles and types to choose from. You'll find round bottles and ones that have flat sides, bottles that have metal or plastic sipping tubes and ones that have a miniature open dish on the bottom instead of a tube. You'll even have to choose between plastic or glass. Selecting a bottle with a sipping tube will eliminate the chance of wasted water or contamination getting up inside the bottle. Opt for the metal tube instead of the plastic one, as your rabbit will make quick work of a plastic tube by gnawing on it. Glass bottles cost a bit more than plastic and can break if they're dropped, but your bunny might be tempted to nibble on a plastic bottle. In the question of glass or plastic, you may want to try a plastic one at first for economic and durability reasons. You can always switch to a glass bottle if she chews a hole in the plastic one.
Cage Mounting Options
The typical mounting method is to secure a water bottle to one of the interior sides of your rabbi's cage with wire or a nut and bolt type system. Some mischievous bunnies can figure out how to detach their bottles, but your rabbit won't be able to effectively drink from a bottle that isn't hanging upright in the proper position. The solution to this problem is to get a water bottle that can be mounted on the outside of your bun's cage, which will also make it next to impossible to chew on. Most may be able to attach from either inside or outside the cage, but to ensure that your bunny won't tamper with her water bottle, make sure to get one that will attach from the outside while still allowing her to access the tube for drinking.
Cold Weather Solutions
If you live in a climate where the winters are cold and your bunny will be living outside, you should have a plan for dealing with freezing water during low temperatures. Water expands when it freezes so you won't be able to fill the bottles all the way to the top, regardless of whether you go with plastic or glass bottles. This means you should use bottles that are larger than necessary for your rabbit's size to ensure she'll have enough water without having to fill the bottle all the way. You may want to have more than one bottle, too. That will allow you to remove one bottle if the water freezes solid and replace it with the second bottle without having to wait for the water to thaw. Alternatively, there are water bottles that plug in and are heated to keep the water above freezing so you never have to worry about your rabbit dehydrating because of the weather.