What did Nancy put in Sykes's drink in Oliver Twist?

In Charles Dickens's "Oliver Twist," Nancy secretly adds opium to Sykes's drink. This act is meant to incapacitate him and assist in her plan to rescue Oliver from the criminal underworld. Nancy’s actions highlight her complex character, torn between her loyalty to Sykes and her compassion for Oliver. Ultimately, her decision reflects her desire to protect the innocent child at great personal risk.