Syke. Or psych. Early 90’s kid slang, had a definition akin to just kidding or fooled you but more mean spirited. Said to mark the previous statement as intended purely to mess with the listener’s mind or psych them out. Similar in spirit to ending a sarcastically spoken sentence with “NOT!” though distinct.

“Yeah man, you can drive my car. Psych! You’re not touching my ride.”

The more I type about it, the less “psych” looks like a valid English word.

Of course it is. Go rewatch a few episodes of “Psych!” to cure yourself.

You know I know that you’re not telling the truth.