It's not the only juice you can get in prison. Mostly orals but even injectables are available. Same goes for recreational drugs..
Paperstuff is nothing new and I don't think that some prisoner had that idea

Was pretty popular in OZ for a while because of the strict customs .. hard to get sth. in there - but they found out about it soon and now even "paperbolics" are not safe to get into OZ/NZ.
Stuff came mostly out of Thailand - Methandienone , Anadrol , Sildenafil , Tadalafil , Clomifen , Anastrozole, Stanozolol etc.. pretty wide range.