Put the fruit in the bottom of a cocktail shaker and bruise it with a muddler or the end of a bar spoon to release some of the juice. Add the sherry and sugar syrup if using.

Fill the shaker with ice and shake hard. This will extract more juices from the fruit and dilute the drink.

Strain into a highball glass, filled with fresh ice and garnish with a slice of orange or lemon and a piece of pineapple.