"Αυτή τρώει φρούτα."
Μετάφραση:She eats fruit.
Normally the noun is used as uncountable, it's the article that shows whether you have, say, a banana, or a bunch of them. I suppose, however, that this case has much in common with "fish/fishes" - in some cases you make it plural in order to refer to some variety of types (in case of fruit, it may be apples and bananas). But if there's no need to highlight it, we get "fruit"