Using the commands
/replaceitem entity @e[type=MinecartChest] slot.inventory.1 apple 1 0
or
/replaceitem entity @e[type=MinecartChest] slot.container.1 apple 1 0
yields an error. Says it cannot replace the item in the chest with an apple. This bug has been going on for 2 versions now, will it be fixed soon?
Do not intentionally duplicate issues.