Sorry, I'm not sure about mushrooms, olives, or kiwi. Fruit juice would probably okay if you were taking it directly from the fruits. Fruit juice bought in stores for human consumption would have lots of sugar, I would think, and wouldn't be good for him.
Of the other items, the only one I'd consider feeding is Kiwi. Mushrooms are nutritionally empty (1 cup will get you a trace of vitamin c and trace of iron but that's about it) and fruit juice is nothing but sugar water with a few vitamins. Diced fruits at least contain fiber, which hedgehogs need and which helps maintain a level blood sugar. Pure juice just spikes the BG because it digest too quickly.