Eat. the. apple. But not yet. Go do something, like read (not TV!), for fifteen minutes, if in fifteen you still want the apple go pick one out and VERY slowly prep it (wash, cut, peel, however you want it) then eat it. The "i can't have it" is only going to make you want it more.
I must say, I wish my evening cravings on were a 100 calorie APPLE :P
As for the question of what I do, I tend to drink a large glass of water and wait 15 minutes, i tend to want something to "eat" because I'm thirsty