Green’s Dictionary of Slang

cookie n.2

1. (US prison) cocaine.

[US]G. Milburn ‘Convicts’ Jargon’ in AS VI:6 437: cookie, n. Cocaine.
[US]Monteleone Criminal Sl. (rev. edn).
[US]Goldin et al. DAUL 49/1: Cookie. Cocaine.

2. (US drugs, also cookee) an opium addict.

[US]D. Maurer ‘Argot of the Und. Narcotic Addict’ Pt 1 in AS XI:2 120/1: cookie. 1. An opium addict.
[US]Wentworth & Flexner DAS 120/2: cookee One who cooks or prepares opium for smoking: an opium addict.

3. (drugs) crack cocaine in its solid, rock form.

Menace II Society [film script] Cocaine has to be turned into what we call a cookie. Then you could break it off and sell it as rocks.