Cut several long strips from knit/jersey fabric. Mine are all about 42 inches long. Some are very thin, others are slightly wider.
Stretch each piece with your hands. The edges will curl up. I call this t-shirt spaghetti.
Knot all the ends together.
Lop off the excess and wear....
...or use a scrap of fabric to wrap around the knot (bandaid style) and stitch to hold in place.
Instant white shirt karma.
I used the same technique to make a headband. Instead of knotting the ends, I sewed them together for a smoother look.
I cut the t-shirt spaghetti very thin and doubled it over to stretch around my head. I sewed a simple jersey 'flower' (a length of jersey stitched into a haphazard circle) and topped it with a vintage button.
Stitch it in place and enjoy.