This task goes hand in hand with the SELF-SERVE task.  It is pretty easy to teach them how to prepare most fruits.

When your preschooler can get up to the sink and get their water, they can get out a colander and rinse all kinds of fruit.  Make sure to show them how to dry off the fruit or set the colander on a large plate so that the fruit has some time to dry.

After proficiently utilizing a butter knife to make and cut sandwiches, they can begin cutting strawberries, bananas, and small oranges.

This may be a task you assign for snack time or soliciting help when you are making meals.  Just make sure that you let them know the expectation before they are given the assignment.