The company I work for sells them, and we pretty much use a little $6 cleaning cloth that A&A sells. It gets them to look brand new and gets most of the tarnishing off. Some of the bracelets do tend to change color from gold to silver or silver to gold but thats all natural change in the metal and can't be fixed unless you purchase a new one. They hold up really well if you take care of them the right way. Don't wear them around chemicals or water and definitely don't leave them where there is a ton of humidity (like in the bathroom when you shower) that causes them to tarnish quicker. And wearing them 24/7 causes them to change color because your body emits chemicals that can make them change as well. Good luck!
Macy's sells an AWESOME sterling silver cleaning cloth that does WONDERS for these bracelets. It made mine look good as new. It's definitely worth it to purchase one and use it for all of your jewelry!
I bought the cleaning cloth that they sell in the store. It made my bracelets look as good as new! On Pinterest there are tons of ways that people say they clean theirs but that can actually ruin the bracelet and take the gold finish off.
I keep mine in some of the bags I've received with my bracelets. They are nice, soft cloths, and help to stop some of them from tarnishing so fast. I would also recommend buying a jewelry cloth to clean your bracelets with once in a while.