Buying or building a shelving unit that can slide in and fit around the toilet is a great use of space. This bathroom hack is perfect for renters because it can slide in and out without damaging the wall.
10 Ways to Squeeze a Little Extra Storage Out of a Small Bathroom
You'd be amazed at how much stuff you can fit into a really narrow cabinet. This particular one wins out over other narrow bathroom cabinets because it has drawers, so you don't have to pull the whole cabinet out every time you want something. I had something similar that I used for years — it tucked neatly in beside the toilet in the tiny bathrooms of four or five different apartments. Bathroom cabinet, $119 from Amazon.