Happy Halloween!

A cup cosy is a basic sleeve, that you decorate. Usually knit in the round.

Use the measuring tape and go around and around the glass like you would a bandage. That will give you a guideline of how long your flat cord needs to be.
And make sure you sew it on with the sleeve on the cup...use a running stitch.
Or you will not be able to get it on the cup when you're done.