Ha! We saved a LOT of money by "pre-partying" on our balcony most of the time.
A bottle of hard liquor and a mixer from Safeway cost about as much as 2 or 3 Aulani cocktails, no joke. If you don't have a car, the ABC across the street has a good selection (not my preferred Hawaiian coconut vodka that Safeway has though). We basically told our kids they had to use the refillable mugs only, b/c by the time you pay for those - buying MORE soda elsewhere is pointless added cost. If you use soda for your mixer and have the mugs, you can even avoid to buy that with your hard liquor. It makes me a bit weak-kneed to think of how much our already-insanely-high credit card bill post-Aulani would have been if we bought our drinks at the bar or in the restaurants nightly.
We also had water bottles with us that we used to fill with our cocktails and bring to the beach or the lawn for the Starlit Hui or movie. I'm making it sound like we did nothing but drink in Hawaii, LOL!! But really, it was a matter of drinking when we were NOT at a meal simply to avoid restaurant drink costs.
If you only meant NA drinks, then definitely get the mugs. They're pricey, but if you use them enough, make tons of sense. We bought two and we adults used them for coffee, washed them, then passed them of to the kids for soda/lemonade for the rest of the day.