Vinegar would probably work, but an emery strawberry is the usual tool for cleaning needles. The sand inside scrubs off debris, and it also helps keep the needle sharp. I give needles that seem dirty a wipe with a tissue in case of chunks, then stab the strawberry until the needle looks shiny. I’ve been told to avoid exposing needles to water, because it can lead to rust. (Not that I actually do, lol, I wet the end of my thread all the time. But I try not to clean them with water or water-based products unless it’s fallen in the cat box or something, and I need to sanitize it with alcohol).

I tried vinegar and fine steel wool and it just made the black part shinier lol