At the parks you can find fresh fruit in many spots, here are some easy to find spots:
AK: Harambe Fruit Market (near entrance to K. Safaris)
MK: In Liberty Square, there's a very small snack market next to Columbia House, and across from entrance to Liberty Belle
DHS: Anaheim Produce, on Sunset, road to Tower of Terror and ther Rock-N-Rollercaoster
Epcot: Sunshine Seasons in Land Pavilion