How to prevent sliced apple / pear from turning brown

If you put sliced apples and pears in your children’s lunch boxes, and your children do not want to eat them, because they turn brown until lunch time, you have 3 options:

1. Put a whole apple or pear instead of sliced apple.
2. Slice the fruit neatly (using apple slicer might help) and put it back together with a rubber band.
3. Rub apples with a little bit of fresh lemon juice.