There's only one real sort of fruit in the game: cherries. The recipe for fruit salad presently calls for an apple, a banana and a bunch of grapes, but it might as well just call for 11 cherries. The same goes for other recipes - having different fruit just delays the process a bit, because you don't need to collect anything but cherries.
I imagine that designing lots of different sorts of fruit trees would be difficult, so how about having fruit trees give fruit *and only fruit* as bonuses. And they'd be big bonuses - you might win a dozen bananas or twenty oranges. This would mean that it would be worthwhile collecting cherries just to get the bonuses, and it would give players an ever-changing random collection of fruit to use for making different cocktails or food.