They are bottom-up seamless bottle socks with stranded colourwork.
This will be a fun project that utilizes a small ball of yarn.
The length can be adjusted depending on the height of your bottle.
You can also attach a string with an I-cord.
There are colourwork charts for Goldfish, Kissing gouramis and ribbon as a bonus.

KNITTING NEEDLES
3.25 mm (US3) a set of 5 double pointed needles

YARN
Fingering or Sport weighted, any scrap yarn in your stash

NOTIONS
1 marker, 1 tapestry needle, 4 beads or mini buttons