Food made of imperishable materials
eg. ice cream made of rock (made with lots of food colouring, possibly paint, mashed potato and some photoshop magic)
plastic toy food
you could argue the stone in a peach is indestructible. The soft fruit around it quickly disappears but it's heart will remain in the soil until it becomes a tree.
Images from Uppercase, The simple things, an interiors magazine from the uni library whose name I can't remember...