Check the airport shops for a wider assortment of juices and bottled drinks, or the restaurants/fast food places that sell to-go smoothies or coffees. The assortment of liquor on a flight is going to depened largely on if it's an International or domestic F trip, and who the carrier is, but with a few exceptions, you won't find a fully stocked bar on even the most premuim of carriers/cabins. Having a really good mixer helps give more options, and almost anything can be mixed with vodka. If you find a good banana mango smoothie at the airport restaurant, carry it on and ask the FA for the liquor (vodka or rum for that smoothie). The Starbucks frappucino bottles have mostly disappeared from USA domestic F but if you can find one in an airport shop, they are *amazing* with Baileys.
Coke Zero, however, is downright nasty when mixed with liquor so don't go there.