In a word, no. Nothing but well oriented work will allow you to improve your voice (unless there is lack of hydration or some physiological problems to begin with, in which case proper hydration or some specific treatment may help).
A lot of things can harm it, though: lack of hydration, smoking, heavy drinking, and extremely iced drinks. Some foods cause flegm (it varies from person to person) that just before singing can also become a nuisance.
Eating and drinking before going to bed (even just water) may cause gastric fluid to reach the throat and cause irritation of the vocal folds.
A visit to a specialized voice therapeut, preferably an M.D., will help identify potential physiological problems, if there are any that may be impeding your progress, and recomend care or remedial procedures, if required. Getting to know your instrument is good advice for any musician, vocalist is not an exception.
(thanks to Todd Wilcox for helping make this answer more useful).