Cut the jalapeño into rings. Put the sugar and water in a pan and bring to the boil. Stir well until the sugar has dissolved. Remove the pan from the heat and add the jalapeño rings to the sugar water and leave to cool and infuse for at least 1 hour.
Dip the edges of the glasses into the jalapeño sugar water and then into the chilli flakes to create a fun decorative effect.
Squeeze 2 limes and cut the third into wedges. Divide the lime juice, lime wedges and mint leaves between the glasses and muddle with a small pestle to release all the flavours. If you don't have a pestle, you can also use a small spoon and crush the mint leaves in your hands, stirring well.
Put a tablespoon of jalapeño syrup in each glass. Divide the rum and mineral water between the glasses and finish with the ice cubes. Serve with a pestle or spoon and your drinks are ready. Add the jalapeño rings for an extra spicy touch, cheers!