I don't think you'll be hurting for choice onboard, they can make anything you want given the ingredients and if you know the formula
In addition to what they explicitly list on the website for wines, spirits & liqueurs (see the dining menus), they typically have:
Lime & Lemon Wedges (not enough to form juice)
Angostura Bitters
Martini Rosso Sweet Red Vermouth
Martini Rosso Dry Vermouth
Aperol
Campari
Club Soda
Sparkling Water (Perrier)
Tonic Water
Mango Juice
Orange Juice
Bloody Mary Mix (or Tomato?)
Tabasco
Fresh Mint
Coca Cola Products (Coke, Coke Zero/Light, Sprite, at a minimum)
Ginger Ale
I might have forgotten a few things, anyone else?