I actually stay away from the fruits except in very small amounts. Fruits have a high concentration of natural sugars. They are fine for the chin, but I find if I give them more than once a week or so my chins develop soft stools. Also, some fruits are natural laxatives, apples, raisins and prunes, in particular. I do give one half of a spoon-size shredded wheat (unfrosted) as a treat several times a week, and sometimes add a small raisin on the side
This seems to be a good balance for them.
Remember, just like with us, too much of anything is not good. All treats, grainy or fruity, should be given in moderation. I try to keep a good balance between the grain treats and the fruit treats, so as not to disturb their digestive system. If I see soft stools, I give only grain treats for a while, unless it is full-blown diahrrea. If that happens I stop all treats until it is clear. If I see the poops getting smaller then I give fruit until it gets back to normal.
Treats are a special thing, NOT a main stay in their diet. We need to all remember that and give them sparingly, no matter how much we want to spoil them