16 stitches and 22 rows using double yarn over stocking stitch on 5mm needles equals 10cm (4").
Please note: The bottle size this will fit is 30.5cm x 20cm (13" x 8"). This pattern allows for ease of fit when bottle is filled with water.
Abbreviations used -
st st = stocking stitch (1 row knit then 1 row purl)
yf = yarn forward (bring the yarn to the back of the work, as if to purl the next stitch BUT knitting the next two stitches together. The return purl row the loop caused by yf is purled. This will cause the formation of a hole and also leaving the same number of stitches on the needle.
tog = together (i.e. k2tog = knit two stitches together)
k = knit
p = purl
st = stitch
sts = stitches
inc = increase (e.g. knitting into the front and back of the stitch before dropping off the right hand needle).
rem = remaining
rep = repeat
cont = continue
Method - Using 5mm needles and both yarns together cast on 32 sts.
st st 2 rows
1 - next row k3 inc 1 st in next st. k to end.
2 - next row p3 inc 1 st in next st. p to end.
Rep the above 2 rows until you have 42 sts on needle, cont without further increases in st st until you have 29cm (11 1/2") ending on a purl row.
To make holes for neck of bottle:
k3 * yf k2tog k3 * rep from * to * last 2 sts k2sts
p the next row also loops made by yf (42 sts still rem). st st a further 12 rows ending with p row.
To make second set of holes:
k2 * yf k2togk1 * rep from * to * to last 2 sts, k2.
p next row p loops made by yf k1 row p1 row cast off.
Make a second side to match using same instructions as above.
To make cord - cut 12 strands of yarn 120cm (48") long (6 in shade a and 6 in shade b). Place all strands together and knot one end leaving a fringe above the knot. Divide the 12 into 3 sets and plait the length of the yarns leaving enough at the end for a knot and fringe to match other end.
To assemble - Place the two right sides together, pin to hold in place. Back stitch the bottom of the cover, oversew the sides. Turn to right side thread the plait through the neck holes.