Re: adding bees to mating nuk
Re drones and mating, isn't it mid winter?
But to the rest of the question, from a practical perspective, there is little to gain by adding bees before the queen is laying. If the bees are added after she is laying they can actually do something useful, ie, feed and cover a larger area of brood.
But if you want to add them now, couple things. If you add bees from the same yard to this nuc, because it does not have a laying queen, any bees of flying age will be inclined to leave it & return to their original hive. They will then tell the other bees they know where there is a nuc that can be robbed. Being set apart for a few hours first will not change that. Robbing bees will not be excluded very vigorously, partly because there is no laying queen, and partly because the bees in the nuc will be confused about who is who cos they've just had a load of bees added from the hive that is now doing the robbing. Robber screens are a deterrent, not an absolute robbing preventer.
Likewise spraying with sugar water could start robbing.
It is possible you could do all these things and still not have robbing, however it is taking a risk.
The safest way to add the frame of brood with bees is to pull the frame from the donor hive & check the queen is not on. Then you give it a kind of light vibrating shake, that encourages the flying bees to leave but the young bees cling on. Then put that into the nuc, they won't rob, and they won't kill the queen. No sugar spray.
44 years, been commercial, outfits up to 4000 hives, now 120 hives and 200 nucs as a hobby, selling bees. T (mostly).