Just so you know, Coke was originally made to clean car engines so it does a lot in the way of cutting through grease and other such stuff. I would think it also would soft the jeans, not so much by removing the dye as softening the fabric fibers.
We used it a lot in the shop to clean battery cables when they were croded from battery acid. (sorry , my spelling is so bad even spell check can't figure that word out)