Page "Bender (Futurama)" Paragraph 31

Although consumption of booze is necessitated by Bender's design and should not be generally viewed as a vice for alcohol-fueled robots, he apparently drinks far more than he needs for energy conversion.

Bender's excessive drinking contributes to his characterization as an alcoholic (" Hell Is Other Robots " reveals that robots can function equally well on mineral oil instead of alcohol, also contributing to the perception of Bender's alcohol use as a vice ).

If Bender is deprived of alcohol, for instance during periods of depression, he ceases to function properly and shows signs similar to human drunkenness, including developing a rusty 5 o ' clock shadow.

As noted above, his disembodied head has survived for millennia with, presumably, no source of alcohol, so it may be that, when a mere head, Bender neither requires alcohol nor suffers from its absence.