Prep your glass: Chill a tall glass or a rocks glass in the freezer for a few minutes.
Cold glassware helps the bubbles stick around.
Muddle the basil: In a shaker, add the basil leaves and lime juice. Gently muddle 3–4 times. You want to bruise the leaves to release aroma, not shred them.
Build the base: Add rum, pineapple juice, and simple syrup if you plan to use it.
Toss in a small pinch of sea salt to sharpen flavor.
Shake briefly: Add ice and shake for about 8–10 seconds. You’re chilling and marrying flavors, not trying to dilute heavily.
Strain: Double strain into your chilled glass over fresh ice to catch basil bits and keep the drink silky.
Top with kombucha: Slowly pour in the kombucha. Start with 3 ounces, then taste.
Add up to 1 ounce more if you want extra fizz and tang.
Garnish and serve: Slap a basil leaf between your palms to release oils and float it on top. Add a pineapple wedge on the rim if you like.
Taste and tweak: If it’s too tart, add a tiny splash more simple syrup. If it’s too sweet, squeeze in a touch more lime or add an extra half ounce of kombucha.