my cat is on a diet?

Green tea is safe for cats and dogs. Yes, you don’t want to go over-board with the caffeine, but that can be handled by either giving caffeine-free green tea, or reducing the amount of caffeine by infusing the leaves in cold water.

The kitty will lose weight IF you feed it kitty food. Believe it, or not, Mr. Kitty isn't human.

It's common for cats and dogs to be able to cause vomiting by consuming an irritant such as grass. They do this to help remove foreign material from their stomachs, such as feathers. Dry foods, such as kibble, can cause this response in some cats, particularly if consumed too quickly. If your cat is on a diet, he may be devouring his kibble at a breakneck speed.

Oh for god's sake, if this is a serious question, all a cat should drink is fresh water!

This guy is trolling you folks.  Literally no one is that stupid.

Tea is not good for cats, also coffee and chocolate.

Don't joke about a cat's diet. Give it a good quality cat food and plenty of water to drink. It can have a saucer of semi skimmed milk but cream is very rich and fatty and neither you or your cat should have it. Cats can also eat fish and chicken chopped up in small pieces and without bones. It will love you for sharing that when you eat it, instead of one of it's meals per day, and that is healthyer for you both.

my sister sometimes house sits for a friend who has many cats. Each morning she gives each cat a desertspoon of normal cream. This small amount should be ok.