Yep.. Sugar is very high in fruit - which can a) induce sugar highs and lows producing excess hunger pangs b) has higher calorie count than vegetables (you're technically not supposed to exceed 800 calories per day on Lite) and c) Acidity (though this is debatable)
Well done FF on abstaining! You will get there for sure, don't worry. While eating one apple won't do much harm to your diet physically, it WILL cause harm mentally on abstinence. So it's best to avoid.
To have cravings for apples is pretty normal, I have them all the time! I crave fruit MORE than cake/chocolate and stuff like that to be honest. I love apples. They're the best fruit ever! I can't have them at the moment through because I can eat a whole bucket of apples in one go - and that's no good either... So no fruit for me until I lose the weight!
But, I do find carrots a good substitute for the apple craving. Not as calorific, not as sweet, but sweet enough and delivers that satisfying 'crunch'!
So when you're allowed fruit on RTM I would definitely advise to stay away from grapes!! I have seen many people post LL (including myself!!) when confronted by them go into overdrive. A few grapes turn into a handful... then two... then the whole pack! After no sugar on LL for so long, the body is just not prepared for such a rush intake. So be careful.