Use Scentsy travel tins maybe? A list of totally feasible ways to organize your entire home." There are some really great ideas here, like the one pictured here. Organize small items in Altoid tins so they don't get scattered around the drawer.
Maybe have a false wall in the back, and use space for storage that is accessible from the outside? SES Welcome to the Outside Found School Bus Conversion Tour! Tons of photos of our finished Skoolie, from living room to kitchen and even full bathroom!
All-in-one: Avanti makes a “complete compact kitchen” that incorporates a (tiny) sink, two electric burners (but no oven), a refrigerator (but no freezer) and even a tall, thin storage space. (Useful in a tiny house or even a guest cottage)