Please watch the "Epitome of malnourishment" series of videos on Youtube... it's a compilation of clips from other video channels on fruitarians and raw vegans. They do no look healthy at all. Emaciated, gaunt, sunken eyes, very prematurely aged wrinkled skin, acne/skin problems, loose teeth - one guy even had a front tooth fly out while talking to the camera.
Can't see how it's sustainable either (unless you live somewhere like Thailand or Hawaii). Most fruit to the UK is shipped in huge containers ships, which have a massive carbon footprint. They're stored in massive warehouses, with high energy costs for refrigeration, lighting, gassed with chemicals to help them ripen (ethylene). An all round massive industrial and infrastructural footprint to bring food to your table, which means high fossil fuel use, mining, concrete, indentured labour in third world countries, pesticides, insecticides, huge demands on the local water table, depriving local people of their fundamental rights to a basic water supply etc etc.
Isn't it far better to eat local, seasonal food from your own bio-region with far fewer food miles?