Plain water in a squirt bottle is useless but vinegar on the other hand

Anything mildly acidic in liquid form cats hate!

White vinegar, dissolvalbe vitamin C tablets, even 100% juices from oranges or lemons will deter a kitty.

Place in squirt bottle and aim for a lickable place. Cats HATE the flavour and smell of it.

Like everything don't try to get it near the face because a cat's face is very sensitive. Even spraying water on the face can *hurt* them.