Depends on what you mean by 'opposite.'
>>4688
If this, then yes.
>>4690
If this, then no.
The first is logical opposition. The second is more about functional opposition. There's nothing you can eat that would end up un-eating an apple.
Though that's amusing to think about. Presumably if there's an anti-apple, there's also anti-eating. Do they cancel, like mathematical negatives? Is anti-eating an anti-apple like eating an apple?
What about the opposite of not an apple, but the event 'eating an apple.' Anti-eating anti-an anti-apple? So throwing up something that's not an apple, I think? It's suitably convoluted, in any case.