When I need to heat up food in microwave, I usually put it in some closeable vessel and pour some water to the bottom of the vessel. Enough that less than half the water comes from food itself. Then I close it and put in microwave. The microwave makes my water evaporate, and the steam heats the food. I find it more effective than having the microwave heat water contained in the food.
TIL this method works well with half-frozen food too.