Syk

Sky is a substance from the Earthforce portion of the Generation 1 continuity family.

Syk is a forbidden circuit booster, presumably the Cybertronic equivalent of an illicit narcotic.

Fiction

Marvel UK comics continuity

Earthforce

Mixmaster dealt syk to his fellow Decepticons (presumably, his chemistry skills allowed him to make it in the first place). Soundwave discovered this during a cursory mind-scan of the passing Constructicon, but didn't narc on him, 'cause S.W.'s cool like that. Secrets

From Teletraan I: The Transformers Wiki, a Wikia wiki.