Most places recommend 2.5 gallons per brigg (or apple snail/mystery snail), because they have such a high bioload. If you are willing to do the water changes it could work in a 1 gallon, though. Oh, and you will need to feed it algae tabs or snello (veggie baby food and unflavored gelatin) because they won't eat plants unless they are dead. I have tons of them, and they will only eat the dead leaves off of the plants.
(Edit: Forgot to mention that they breathe air from the surface, so make sure they have access to it. Also, they can and usually will try to leave the bowl at some point. They can survive outside of water for several weeks, so keep a lid on the bowl, with holes to keep fresh air available.)
They REALLY love algae tablets, though. Here is my boy Jules when he was a wee lad.