- "I don't eat meat."
"Why not?"
"It disagrees with me."
"How about cyanide? Does that give you the rumbly tummy, too?" - ―Arnim Zola and Chester Phillips[src]
A Cyanide Pill, also known as suicide pill, is a little capsule containing a poisonous substance designed to be ingested deliberately to quickly end his own life.
History
During World War II, cyanide pills were common between spies. As such, after killing Abraham Erskine, HYDRA agent Heinz Kruger tried to flee using a HYDRA Personal Submarine. Steve Rogers pursued him and successfully avoided Kruger's escape, but before he could be questioned, Kruger swallowed a cyanide pill concealed inside a fake tooth, dying shortly after menacing Rogers about being the first of many HYDRA members.
When S.H.I.E.L.D. Agents Phil Coulson and Melinda May were trying to capture and interrogate former agent Richard Lumley in Mexico, and interrogate him about her partner Agent Linda Avery, Lumley tried to consume one of these pills concealed in his watch before he was captured, fearing Coulson and May wanted to torture him, as he was shown to be very relieved when they identified themselves as Agents of S.H.I.E.L.D.