The following sentence is in the active voice: "Do not smoke."
What is its equivalent in the passive voice?
1- Let the smoke not be done.
2- Smoking is prohibited.
"Smoking is prohibited" is a very common formulation, e.g.
Note that this is not a passive version of "Do not smoke", since this sentence cannot be transformed into the passive voice. It is an imperative form that has neither an explicit subject, nor an explicit direct object.
The form "Do not be smoked" (from a comment by Colin Fine) is unusual and would not be addressed to a smoker but to something that would undergo the act of smoking.
Quite simply the passive is:
Do not be smoked.
Remember that passive reverses the roles of object and subject. You are no longer the one doing the smoking in passive voice.
To use @brianpck's example from his comment, "do not be deceived" implies that someone is potentially deceiving you, while it's active counterpart, "do not deceive" implies that you are potentially deceiving someone else.
If you want to preserve the meaning then you would have to expose the implied direct object (and imply the subject), but an imperative statement is necessarily directed at the second person (usually not an inanimate object), so it's not really possible.
The best you could do is look at that cigar square in the face and tell it:
"Hey cigar, do not be smoked"