Place 8 fresh mint leaves in a sturdy mixing glass or cocktail shaker. Add the simple syrup and fresh lime juice. Gently muddle the mint 6–8 times — just enough to bruise the leaves and release aromatic oils without shredding them.

Add rums and fruit juices

Add the Malibu rum, light rum, guava nectar and pineapple juice to the shaker with the muddled mint mixture. Add crushed ice (about 1 cup). Secure the shaker lid and shake vigorously for 10–12 seconds until well chilled.

Assemble & Finish

Strain and build

Fill a highball or Collins glass with fresh crushed ice. Double-strain the shaken mixture into the glass (use a Hawthorne strainer and a fine mesh if available) to keep mint bits minimal.

Add grenadine and soda

Slowly pour the grenadine down the inside of the glass so it sinks and creates a layered effect. Top with Sprite (about 3 oz) poured gently to preserve bubbles. Give the drink a very gentle stir (1–2 turns) to marry flavors while keeping some layering.

Garnish and serve

Garnish with the remaining 2 mint leaves slapped between your palms to release aroma, then placed on top, along with a lime wheel and pineapple wedge on the rim. Serve with a straw and a cocktail pick if desired.