Can cats drink milk?

Best not. Kittens can digest milk, but most cats lose much of that ability as they grow up, and milk then tends to cause loose stools, wind or an upset stomach. It also adds calories without adding anything a cat actually needs.

Water is the only drink a cat requires. If you want to give something special, choose a treat made for cats instead.

The long version: The first week with a kitten

General guidance, not a substitute for your vet. If your cat seems unwell, call them.