Syk

Syk is a forbidden circuit booster, presumably the Cybertronic equivalent of an illicit narcotic. In the somewhat confusing Earthforce continuity, Mixmaster dealt in the substance (presumably, his job as a chemist is what allowed him to make syk 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.

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