When people talk about empties, they mean bottles or glasses that used to have a drink in them, but are empty now. You hear it at home and in pubs: “Take the empties out” means take those used bottles to the recycling, or back to the shop. In some places the shop gives you a little money for each empty bottle you return. The word is informal, and it is almost always plural. Though actually, this is a noun here — the empty things themselves — not the verb in “he empties the bin.” People do not usually call an empty box or an empty room empties; they mean drink bottles and glasses.

空瓶、空杯（喝完要回收或退瓶的那些）