Most people need a minimum of six hours sleep out of every 24. A character who goes without this amount of sleep must make a Vigor roll at a cumulative -2 every 12 hours thereafter (maximum penalty of -6). A large amount of coffee, soda, or other stimulant adds +2 to the roll.

• Recovery: Every four hours of restful sleep removes a level of Fatigue.
• Incapacitation Effects: A character who suffers this much Fatigue simply falls into a deep sleep for 2d10 hours.

Savage Worlds Deluxe Edition p. 103