I made a water bottle carrier for my friend, and while I winged it while I went, I wrote down the basics of how it went. This water bottle was one of those tall Camelbaks, but you could adapt this pattern for any water bottle.
Worsted Weight Yarn, less than 170 yards
6 SC into Circle, tighten and join with a SS to first SC, CH 1 (6)
*2 SC into each SC all the way around*, join with SS to first SC, CH 1 (12)
*2 SC into first SC, 1 SC into next* all the way around, join with SS to first SC, CH 1 (18)
*2 SC into first SC, 1 SC into next 2 SC* all the way around, join with SS to first SC, CH 1 (24)
*2 SC into first SC, 1 SC into next 3 SC* all the way around, join with SS to first SC, CH 1 (30)
Continue in this pattern until same size as the bottom of the water bottle. You will no longer join at the end.
1 SC into each SC all the way around, not joining, until base of carrier goes up 1/2 inch around the water bottle.
*1 DC into next SC, CH 1 and skip the next SC* continue until reach all the way around bottle. Do not join.
*DC into next chain space, chain 1, DC into next chain space*until carrier reaches desired height.
Remember the loser you stitch the more the carrier will stretch when holding a water bottle that is full.
*HDC into each chain space all the way around* SS into first HDC.
HDC 6 (or desired width of carrier strap) CH 1 and turn
*HDC into each HDC, CH 1 and Turn*repeat row until strap is desired length
SS to other side of carrier, fasten off and weave end.