I'm all for knitting and crocheting both fun and/or functional items. Not all knitting needs to be functional, it can be weird or cute or silly.
But then, there's just madness.
Cozies for your fruit serve no purpose. Apples and bananas do not need a sweater.
A cozie for beer or coffee cups can be, in certain circles, a bit of a stretch. Beer bottle cozies help keep beer cooler longer, and don't get your hands cold. One might argue that the purpose of an ecological, reusable coffee cup cozie seems pointless when getting coffee in a paper cup that you're going to throw out anyway - but they can be cute nonetheless, and they do serve a purpose.
Apple cozies serve no actual, functional purpose. Unless, of course, your goal is to have your coworkers stare at you in the lunch room, wondering why your apple is wearing a sweater. Or, maybe, you've got a partial skein of yarn that's just burning a hole in your craft room and there is absolutely nothing else in the universe that is left for you to make a cozie for. Or, maybe, pharmaceuticals are involved, and while on them you become convinced that your apple is freezing and needs a sweater. Or, maybe, you're trying to be an etsy hipster and you've already got pictures of you posing with that Sharpie marker mustache you drew on your finger, and making an apple cozie is the next logical step in things to make and display online.
I'm usually the last one to comment on the utter uselessness or tackiness of something. Nevertheless, comment has been made. I've yet to be convinced of their purpose, and can guarantee that this will never be something that I'll make.