Microwave them with a bowl over the top of the plate there on or a plate over the top of the bowl they are in, and if necessary sprinkle a little water in.

Or if you are truly dedicated to the craft, got a steamer basket for a pot, and boil your choice of a half inch or 1 cm of water in the bottom of the pot, put the fries in the steamer basket, and put a lid on the steamer.