Put the sugar with 50ml cold water in small saucepan and cook over a low/medium heat (don’t let it boil) until the sugar has dissolved. Set aside to cool completely.
When cool, put the sugar syrup in a medium pouring jug with the gin, lime juice and tonic water, then mix. Put a cucumber slice and a raspberry into each of the lolly moulds, then pour the mixture evenly into the moulds. Add the lolly sticks and put in the freezer. Freeze until solid (ideally overnight).