Cats barking at five or six in the morning may be caused by reasons such as hunger, thirst, boredom, or the litter box is too dirty. Generally, this happens to kittens, so you need to prepare sufficient cat food for the cat. and water, and clean the litter box before going to bed the first day. You can also prepare fur ball toys for the cat to play with, so that the cat will not disturb the owner's sleep in the morning.