Although there are some consumable items that help reduce SLP deprivation, attempting gameplay without sleep may not be possible unless you are prepared to skip a few quests that require sleeping. The effects of not sleeping, that is surviving on caffeine based consumables or chems, is uncertain, however, no known ill effects have been reported.
In Hardcore mode, Completing the initial quest of any of the DLC packs will bring your SLP meter to 0 and disable it.
pcps3xbox360 Sometimes the SLP meter on your Pip-Boy 3000 can get stuck on zero, and in fact will not display any number below the indication arrow. This is normally caused by travelling through canyon wreckage, which sets all hardcore meters to zero. During this time your character will not advance in sleep deprivation. This bug may be fixed by finding a bed and sleeping for any amount of time. After the player wakes, the gauge will display the number and resume its normal function. [verification overdue]