I laid the bottle on the fabric, traced round it leaving a half inch seam allowance then cut out a matching pair of fabric pieces.
With wrong sides facing, I sewed the sides from neck to bottom before flipping fabric right sides out and sliding in the bottle.
On one version I hand stitched the bottle in permanently, on the pictured version I used kam snaps to close up the bottom. With IKEA fleece I don’t have to worry about hemming the exposed edges.
This is a huge success as it keeps the bottle water hot for longer and is nice and cuddly too. Great return on the time spent on this one.