The Brief: Crank is a low-purity, altered form of methamphetamine, aka meth.

DEEP DIVE
Synonyms: Crystal, ice, tina, glass, quartz, tweak
Crank is a low-purity, cheap form of crystallized methamphetamine (or crystal meth). The term is often used synonymously with meth, crank is actually a more potent form of meth, often described as “Poor Man’s Meth”.
Someone high on crank or meth is said to be tweaking.
Rum, whine, brandy, coke, marijuana, crack, crank, acid–.. Oops. I was naming off drugs when I was naming off booze. Sorreh.~
— Namie Blackhart (@Namie_Ebooks) March 14, 2019
Methamphetamine can be taken orally, snorted (in powder form), smoked, or injected. Crank, which is administered in a powder form, can be used much in the same way as pure methamphetamine.
Meth is a stimulant that creates incredibly positive, euphoric, and alert feelings over a period of several hours. However, it is also an extremely addictive stimulant.