They are all the rage on Etsy since the Curiosity Shoppe brought them into the hip and green mainstream, so I thought I would offer up two versions of my own, with and without the actual knitting.
Version #1: Work with What You Got
1. Take any old sweater or legwarmer with a fun pattern or nice palette and cut it into an 8″ x 3″ Rectangle (adding seam allowance for top and bottom hems as desired and for your connecting seam).
2. Use an overlock or zigzag stitch around all four raw edges to keep the knit from further unraveling.
3. Fold over the top and/or bottom create hems as desired and overlock or zigzag hem.
4. Bringing right sides together, make final seam by overlocking or zigzagging the two short ends together to make a cylinder.
Voile! Your coffee is warm and you have an excellent homemade green gift.