Feed it often, and give it some water. Make sure to keep it warm. The formula is a good idea. If needed, call a vet, they will be a good source for information. Good luck with your new "baby'!
As long as it doesn't have worms, and you get it rehydrated, it will probably pull thru. You'd be suprised what a cat can go thru and survive (having had several families of them live in our barns). Rescued a few myself in my younger years. Wait. Am I old enough to be saying that?? <shudder>
You need to make them go to the bathroom BTW, remind them I guess. They won't do it on their own. Use a moist cotton ball to wipe their "areas" and that should do the trick. Call a vet or pet refuge and they will direct you to a source of formula.
Edit...I took it off...I Love animals..Ferrets, Dogs....you name it...
I suppose it was in bad taste... Don't want anyone geting the wrong impression of me....
I fed baby squirrels and rabbits with baby formula before and got them big enough to release back into the wild..
That cat will be just fine!
I once saved a cat that was trapped under a dock following a bad storm...I kept hearing a faint "meow...meow..." and I had NO idea where it was coming from. Finally I lowered myself down head-first to get a peek...poor thing was pinned with her head barely above water and sometimes going under. I lifted the dock as hard as I could and behold...little kitty was free! I scooped her up and with the help of a few friends was able to bring some life back into her.