I prefer the small plasic storage boxes from Rubbermaid. You may also keep them in any suitable tight container from Aquariums to custom built cages. The most important thing is that it must be escape proof. All Cages should be kept with newspaper, Paper towel or a card board liner. These liners absorb waste and keep snakes dry.
Garters depending on their diet and time of year can mess a lot.
So I clean all my cages two times a week. All Cages need a small bowl of fresh water , that is always kept clean. Garters can be kept at a wide range of Temps. For example I live in Florida and My Garters live on my screened back porch year around. Somehow or another my snakes thrive.