Heating up leftover French fries in a toaster oven will give you a crunchy, delicious snack or side dish. A toaster oven won't heat up the kitchen as much as a standard oven, and it uses less electricity, making it an efficient appliance for reheating a small number of fries. The key to properly reheating French fries, whether they are homemade or brought from a restaurant, is to cook them for a short amount of time at a high temperature so they don't have a chance to dry out.
Place the toaster oven rack in the middle position and preheat the oven to 400 degrees F.
Lightly spray a shallow baking dish with cooking spray, or cut a piece of parchment paper to fit in the bottom of the dish.
Spread the French fries out in a single layer in the baking dish.
Put the fries in the preheated oven and bake them for two to three minutes, or until they start to brown. Put on an oven mitt and remove the dish from the oven. Flip the fries over with a spatula and put the tray back into the oven for another two to three minutes, or until the fries start to brown on the other side.