Rub a lime wedge around the rim of each margarita glass, then dip the rim in red sanding sugar and set aside to dry.

In a large pitcher, combine the tequila, triple sec and fresh lime juice, stirring well.

Add the pineapple juice and stir again; the mixture should taste sharp and citrusy, with the tequila clearly present under the fruit.

Refrigerate the base for at least 30 minutes.

Just before serving, stir in the lemon-lime soda, then pour over ice into the prepared glasses.

Garnish each glass with a lime wedge and a mini candy cane propped on the rim.