Agua fresca

Put the sugar and 150ml water in a small pan. Bring to the boil over a medium heat. Reduce the heat and simmer for about 3 minutes, stirring occasionally, until the sugar has dissolved. Remove from the heat and set aside to cool to room temperature.

Peel the cucumber, slice in half lengthways and use a teaspoon to scoop out and discard the seeds. Cut into roughly 2.5cm chunks and put in a blender or food processor with the mint leaves; whizz until smooth. Strain through a sieve, using the back of a ladle to press down on the pulp and extract as much juice as possible.

Pour the strained cucumber juice, sugar syrup and lime juice into a large jug and stir well; add plenty of crushed ice and the mint sprigs. If serving with tequila, add a 25ml measure to each glass with ice and top up with the agua fresca.