There is no street name, per se, for caffeine, as there is no need for one. Usually street names are used to cover up illicit drugs or substances, where caffeine is neither illegal nor illicit.
Boomers.
Ecstasy
Magic Mushrooms, Shrooms, Liberty Caps, Mushies, etc...
a kind of marijuana or a street name for the drug Datura
Shrooms, mushies, magic mushrooms, cubes (in the case of psilocybe cubensis)
Heroin
Illicit is not the name of a specific drug. The word just means illegal, so it would refer to any illegal drug. That would include cocaine, marijuana (depending on the location), crystal meth, speed, PCP, LSD, etc.
You've failed to mention it's name or chemical composition.
Speed is the street name for Amphetamine, and Methamphetamine which are drugs.
Well, speed is the street name of a type of drug, do you mean what other street names mean speed?
Goey is an Australian street name for speed (amphetamine).