Revealing mistake: When Robocop is on the bike, he does a skid. in the exact place where he does this, there is already skid marks from previous takes.
Revealing mistake: The Mayor looks into the armoured van at the money, and picks up a gold bar. It looks bad, is obviously too light to be gold, and doesn't clink when put back.
Continuity mistake: When "Robocop 2" goes beserk, he shoots several civilians and a row of OCP security. The last civilian to be hit in that scene is later seen being helped down a flight of stairs by two folks as the President of OCP talks with some of his subordinates about who to lay blame on for the incident.
Answer: We're never given specifics about it, but we do know it's the most addictive drug in history.