I originally made this to be served with gin for a cocktail party I threw for a friend's birthday. It's also great without the gin, though; the dash of apple cider vinegar gives it a tangy kick. The frozen blueberries will keep the drink colder longer, adding their sweetness gradually to the drink as they thaw. They make a nice sweet crunch to nibble when you're finished!
This can be made with either club soda or ginger ale. I prefer it with club soda, but some people prefer the drink a bit sweeter. - Syronai —beyondcelery
Test Kitchen Notes
Imagine it's 100° F with 90 percent humidity; the air is still and sodden. You are hot and sticky, and even breathing requires effort. What you need is a nice, cold drink. You whip up a batch of Cucumber Fennel Fizz. It is the perfect blend of tangy and refreshing. The cucumber is the standout flavor with a hint of fennel in the background. The lime juice and vinegar add a nicely sour edge. The fizz makes everything livelier. You feel invigorated; you can once again face the world. Thanks, Syronai, for a perfect summer cooler! - hardlikearmour —hardlikearmour
Skin cucumber, cut into 4 chunks, and toss into blender.
Add lime juice, apple cider vinegar, ice, and 1-inch fresh fennel. Add gin if using. Blend until smooth and foamy, about 2 minutes. Don't be tempted to add more liquid unless your cucumber is exceptionally dry and it refuses to blend. (In which case add a dash of soda.)
Split the cucumber mix between two glasses, adding either club soda or ginger ale in a 1:1 ratio. Add 5 frozen blueberries to each glass. Garnish with a sprig of fresh fennel.