Sports mouthguards can be custom-made from an impression of your teeth or bought ready-made. Ready-made mouthguards are usually softened in warm water so that they can take on the shape of the teeth. If you wear braces, you can use this kind of mouthguard, as it will not damage them and will still be easy to take out after use.
This answer is for general information. Your own case needs an examination by an orthodontist.