Rectangular Water Container's Cap

I was a bit unwell last week and took a couple days off. I took the chance for a major kitchen cleaning and a simple sewing project. A cap for my Tupperware water container! It is waterproof from the outside (because I use oilcloth) with cotton fabric lined inside. I slipped in a thin rubber band around the edge so it will securely fit it in place and for more convenience regular use.

If you have a rectangular head, you may need a rectangular shower cap like this. Haha!