‼️ Vet tech friendsssss!! I need you!

My little sister in law found two small kittens in her yard. She doesn’t know how young they are and they aren’t eating or drinking. They don’t have cat food right now so my little sis in law tried feeding them hard dog food 🤦🏻‍♀️. I told her for now soak the dog food in water and mush it up to see if they eat it just until she can go get wet cat food. They also have fleas. I doubt she will bring them to the vet and I’m pretty sure she’s going to try to keep them. She’s 12 years old.

So what can we do?? How young is too young to use flea treatment/shampoo? What product do you recommend? Should they be drinking milk or water?

Anything else we should know?