Sardines are ok as an occassional treat in your kitties' healthy diet! I sometimes get my girls a little can of No Salt Added Sardines in Spring Water, and they adore them!
I bought my kitties a can of sardines a while back as a treat, but they weren't interested. I had a lot more luck with canned tuna. I've also heard good things on the forum about canned salmon, but I've never tried it.
My girls also enjoy sodium free canned salmon, but not nearly as much as when I get them fresh fish from our local seafood market to bake for them! Sierra's favorite is Mahi-Mahi!
If it comes with bones, you want to be quite sure to remove them prior to serving to your babies.
I bought a can of food(maybe Wellness) that was Sradines & something else. Twitch wouldn't touch it. Lily sniffed it, picked up the can, walked over to the litter box & dropped it in. I think that was her way of subtely hinting she thought that food was poop!
I give Lily & Twitch a little tuna on top of any dry food or canned food the first time they get a new gflavor & when I am changing foods. Lily doesn't mind red salmon, but Twitch won't eat it. They both love pink salmon. Mom & dad get mad when I feed the cats the last can of their pink salmon!