Apple was not really the cause of Adam and eve's sin because, apple is God's creation. what he created he makes wonderful and also to be a blessing and not a curse to mankind.
And know that we cannot condemn Gods creation, the sin that was committed by Adam and eve is the act of disobedience to God. For the fact that an instruction was given to them by God and they refuse to abide by that instruction, that's the cause of there sin. I believe God has a reason for that instruction, he has his own purpose, so know that he was not purposely condemning apple.
The worst thing that can happen to a man is if a man disobeys God, you can disobey other things and go free but not God. There is always a wages for sin and there is also repercussion for every sin we commit, we might think that God doesn't see us when we sin but he sees even the hidden one in ones heart, that's why we must abstain from everything called sin in our life because every disobedience leads to sin. So today in the world many people still thinks it's the apple Eve gave Adam and they both ate was the main reason for there sin against God. We should know that God hates disobedient children.