Which literary device is used in this sentence Brutus could have eaten a thousand nails for breakfast and an army truck lunch.?

The literary device used in the sentence "Brutus could have eaten a thousand nails for breakfast and an army truck lunch" is hyperbole.

Hyperbole is an exaggeration used for emphasis or humor. In this case, the sentence is clearly an exaggeration, as no human could possibly eat that much metal. It emphasizes how tough and strong Brutus is, using humor to highlight his strength.