Why do french fries taste awful when reheated in a microwave?

Adding to David's answer, the reason you want to cook fries outside-in has to do with water. When you cook the outside first, it evaporates the water on the outside, and that water either leaves the fry (goes into the oil and makes bubbles of water vapor) or is driven into the fry, where it makes the inside soft. read more

It’s actually more of a texture issue than one of taste, and that is because in a microwave you are actually reheating the fries by steaming, and there is no way you will ever achieve the desired crisp texture (unless you use a special microwave “crisping” mat or tray similar to the gray sleeves they used to have with Hot Pockets). read more

Fry everything or put it in a toaster oven to reheat. Add a little butter or water depending on the food and most everything including Mac n cheese and French fries are reheated deliciously. read more