Some people notice that they can have bad breath with braces. There are a few causes of bad breath but the most common one comes from food stuck around the braces and in between teeth. When you don't brush and floss your teeth well, plaque, which is made up of bacteria, collects on the teeth. These bacteria can lead to bad breath.
Not to worry though! The best way to control bad breath is to brush at least twice per day, floss around your braces, and use mouthwash. Try a few different kinds of toothpaste to see which one you like best. From my personal experience, Aquafresh Extreme Clean toothpaste is effective to give you minty breath and Breath Rx or Act mouthwash works well in addition. Mouthwash alone isn't going to cure any bad breath problems - so make sure you brush and floss well. See this post on How to Keep your Braces Clean