"I sleep in what I work in."
Translation:Abban alszom, amiben dolgozom.
Since the noun is not named in the first clause, we use "ami".
Compare these two sentences:
"Abban a ruhában alszom, amelyikben dolgozom. - I sleep in the clothes in which I work.
"Abban alszom, amiben dolgozom." - I sleep in what I work in.
"Amely" and "amelyik" have to refer back to a "named" noun.
"Ami" refers back to an "unnamed" noun. Or it refers back to the whole clause:
"Egy irodában dolgozom, ami jó nekem." - I work in an office, which is good for me.
The "named noun" can be in a previous sentence, in the context. It does not need to be in the same sentence:
Q: "Melyik ruhában alszol?" - Which clothes do you sleep in?
A: "Abban (alszom), amelyikben dolgozom." - (I sleep) In the ones that I work in.