There's a lot of good answers for this, I do enjoy sugar-free sports drinks, tap water (columbus has good stuff, surprisingly) milk, smoothies, fruit juices, tea...
But you said favorite. And refreshing.
my heart lies where it lies, and it's always going to be non-alcoholic beer.
It's helped me stay sober for over 8 years. The market has exploded as of late and there's all the variety and detail that craft brewing has been experiencing the past 15 years. I do not drink much soda any more.