Could add a hole in the bottom and make it into a small planter
On this project, the materials used are recycled materials like small milk cartons and old plastic food containers. See video and written instructions here==>
Looking for a concrete DIY to try? Check out this DIY concrete vase idea that uses a mailing tube to create a minimal modern piece of home decor.
Concrete Plan: How to Make a DIY Concrete Vase with a Mailing Tube - Paper and Stitch