The thongs I use for sport with leggings and work are a mix of polyester and spandex. I want them to last as long as possible.
I experimented a bit with one: I made a baking soda paste, applied it to the stained parts, let it sit for an hour, hand scrubbed it, rinsed in cold water, pressed the thong to get rid of as much water as possible, let it to air dry. Am I being too careful?
Baking soda removed all stains.
Do you only hand wash your undies?
I have clothes that I keep out of the dryer, but I’m willing to put pretty much anything in the washing machine (aside from dry clean only stuff). I will hand wash my workout clothes, mainly in the summer, when they are drenched in sweat and I don’t have enough dirty laundry to make it worth putting them in the laundry right away. I just put a little splash of laundry detergent in the sink with some cold water to wash them, then hang them to dry. But I do that to keep them from getting stinky, not to prolong the life of the clothes.