Well, without reading the actual fanfiction, it's hard to say precisely. 'Sakura' is a common name in many fictional works, especially in anime - inspired fanfictions. The 'apology' part could be about her making amends for something she did wrong, perhaps in a relationship or a group setting. And 'lemon' might be used in a symbolic way, like a sign of something that has a bit of a bitter or difficult aspect to it.
In this 'sakura's apology lemon fanfiction', it could be that Sakura has wronged someone, maybe a friend or a love interest. The apology might be a central part of the plot where she has to overcome her pride or some other obstacle. The 'lemon' aspect could be adding a touch of complexity, perhaps it represents a memory or an event that made the situation more difficult. It could also be that the fanfiction is set in a world where 'lemon' has a special meaning, like a type of magic or a cultural reference that is relevant to the apology.