Because the Fennec Foxes primarily live in the desert, their diet varies. This is primarily due to the fact that the food options for these mammals are limited to what is available to them in their environment, which can sometimes be scarce. Their diet ranges from insects and small rodents, to roots, leaves, and fruit (Smithsonian National Zoo).
There are a few things that influence their diet. The diet of the fennec fox changes drastically if they are held domestically. One study observed the diet of wild fennec foxes in three different locations in the north-eastern Algerian Sahara for the period of a year. This study observed that the main diet of the fennec foxes consisted of insects (such as Coleoptera), small mammals, and plant material. As mentioned in the study, the “main diet” of the fennec fox was due to the fact that those were abundantly found in each site compared to scarce items such as arachnids and birds (Brahmi et al). Wild fennec foxes can also go a long period of time without drinking any water, due to lack of access to it in the desert. However, plant matter serves as their main source of water for them, it has been noted that these make up nearly 100% of their water source (Treehugger).
When domestically held, these foxes are, or at least should be, fed an exotic canine diet that consists of high quality canine food. Items such as vegetables, eggs, rodents, etc. are commonly fed to domestic fennec foxes. Because they are being held as pets and do not need to adapt to living in the scorching heat of the desert, domestic fennec foxes should have water available to them (McRee)