How to identify galvanised and stainless cables?
If you really want to test, you can cut a small piece of cable on each and put them in bleach.


Stainless steel would corrode with rust forming evenly.
Galvanised steel would mostly corrode on the cross-section of the cable (where the cut is made). The (correctly) galvanised area will likely to be white.


A little note:


For your time testing, just buy a better cable from a reliable shop next time
The reaction may produce harmful gas, don't put them indoor or unventilated area