I made this cosy for my new water bottle back in April and was waiting to re-test and write out the pattern I used. It was my first project in Tunisian/Afghan crochet and then my second (with some improvements in design) came the following day when I made a cosy for my mom’s new bottle.
The re-testing is just too far down my list of priorities at the moment, but someday it will come!
Riotflower's Realm 
This is nice! I made up a crochet version for my water bottles recently, too … but I like the way your Tunisian crochet looks. I’m going to have to learn that one of these days!