No microwave on the plane.
Boiling water yes..for coffee tea etc,

It is quit easy.

Since I fly every 2-3 months from OZ to Canada.. 24 hours there.
I get boiling water in bottle and then cool it down with water from the tap. As if you wait till the water cools down.. baby is already really hungry etc.
I am not overly concerne with germs on the plane.not much you can do about it. the air is circulated back into the plane.. so germs are well everwhere as it is.