This is messy, so you might want to do the painting part outdoors. We used a water-soluble non-toxic chalkboard paint. You can find chalkboard paint at a craft store. We removed the paper label from the baby formula canister, and Emily covered the outside with the paint. It takes about two coats.
Once the paint is dry, glue some ribbon around the top and/or bottom edge of the canister. Emily loved drawing on hers, erasing it, and drawing again!