Caffeine and Night Shift

Product	Caffeine Content, mg
Espresso coffee	120
Regular coffee	103
Jolt Cola	72
Instant coffee	57
Black tea	53
Most sodas	35-55

Use of 4 mg/kg of caffeine at 12:20 and 1:20 AM effectively to decrease sleep tendency on night shift, enhance performance of subjects during the first 2 nights of string of night shift and did not disrupt daytime sleep. 
 

Reference:
Circadian rhythm, shift work, and emergency medicine.
Ann Emerg Med. 2001;37:88–98.