"What is your job?"
Translation:Sizin işiniz ne?
As I understand it, the difference you are seeing is whether the verb is a separate word--like "drinks"--or a suffix--like the copula for "is." Because you (generally) don't add a suffix for the 3rd person singular copula, it looks like the verb is missing.
O ne içer? = O (subject) + ne (object) + içer (verb) = He + what + drinks
Sizin işiniz ne? = Sizin işiniz (subject) + ne (object) + ____ (verb suffix) = Your job + what + is
In contrast, "What are you?" would use the 2nd person singular copula suffix. "Sen nesin?" = Sen (subject) + ne (object) + sin (verb suffix)
Ne is just nedir whit the later part dropped. Ne is informal, while nedir is more formal and polite. Actually, this sentence sounds a little bit wrong. I would rather translate "What is your job" as either "Senin işin ne?" or "Sizin işiniz nedir?(Here "Siz" is not the second plural, but the respect form of the second singular) "