I wrote a free pattern for a scrunchie knitted either with 2mm, 3mm or 4mm double pointed needles and some yarn leftovers. You can find the pattern on ravelry (link in comments)
PATTERN the Wavelet Scrunchie DIGITAL DOWNLOAD Knit - Etsy
free pattern: kestrel scrunchie – Quince & Co.
Scrunchie
Knitting tutorial : Duo of gourmand scrunchies | Knit On