I think the OP is saying the menu describes the champagne on offer as having notes of apple. That is different from having a flavored sparkling beverage (or the cheap PDB stuff).

To the OP: lots of fancy wines and champagnes are described by wine enthusiasts of "having notes of" or "tastes of" various things -- different fruits, spices, even things like smoke or leather. These are all natural byproducts of the winemaking process and don't mean anything has been added or flavored in the wine. Delta's D1 international champagne -- once up at altitude, not the cheaper stuff served pre-departure -- is a perfectly respectable champagne offering for international business class.