Take them to the grocery store where they can pick out fruits themselves after holding and smelling them. This will increase your awareness of their preferences, as well as providing an educational experience for them. If a green apple meets with a sour face, try a red. The color change might make a difference. Maybe mandarin oranges, rather than the typical navel orange, will interest them.
Seedless grapes are quick and easy, too.
Try dried apricots, raisins, cranberries or a blend of dried berries. Non-sweetened applesauce is tasty, and it's easy enough to throw in a lunch box. Even the flavored applesauces are better choices compared to some of the sugary junk food that kids eat. Don't put your nose up at canned fruit. If your child will eat it, serve it.