How to wash a woven nylon band?

*Buy a cheap soft bristle toothbrush.

*Mix a solution of warm water and gentle fabric soap.

*Use toothbrush to do a light scrub with just warm water.

*Dip the wet toothbrush in your warm water/fabric soap solution and scrub the band front and back.

*Rinse the band in warm water until suds are gone.

*Dab the clean band with a dry towel and air dry (or you can blow dry it if you need it in a hurry)

No damage or fading should occur like this- hope it helps!

The suggested way to wash the woven nylon bands is:

1. Wipe the band clean with a nonabrasive, lint-free cloth. If necessary, lightly dampen the cloth with fresh water.
2. Dry the band with a nonabrasive, lint-free cloth before you attach it to your Apple Watch.

Cleaning your Apple Watch - Apple Support

I think the important thing here is to make sure that it is properly dried after cleaning. If water alone does not clean the band, it might be possible to use fabric soap, although be careful not to use too much.

A soap shouldn't damage your watch strap, but do make sure it has no harsh chemicals like bleach in it. I would suggest treating the nylon strap similar to any other nylon material (like clothing or a bag), and clean it with some soft soap based product to begin with.