Adding sugar at the end of the mixture for apple bread
It is a bit of a guessgame without having seen the exact recipe, but applebreads tend to use rather robust recipes. So there is a very good chance that you will not notice much of a difference. 

If the batter was on the dry side, you might get undissolved sugar. This will give you a grainy texture, possibly you will also perceive the applebread as drier, but the second effect can be subtle. In any case, it will be perfectly edible - it is just that, if the sugar is undissolved, it will deviate from usual expectations. Whether this is a problem or not will depend on the individual eaters.