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.

Because it started in grade school, and grade school kids were not aware of the word “psych.” So they spelt it how it sounded. Sike or syke, they’re both equally incorrect, but the point is the kids who used them were using them correctly.

The only thing remotely weird about it was when they learned the word “psych” and thought they meant two different things (like they don’t believe “psyching someone out” is a thing, like it does not click for them).