Let the raspberries thaw lightly, chop finely in a blender or with a magic wand.
Then pour the raspberry purée into a bowl, stir in the powdered sugar and lime juice.
Let it steep in the refrigerator for at least 1 hour. Stir from time to time.
Pour the mixture into a large jug and carefully pour in the well-chilled mineral water. Be careful, something foams up in the process. If you only have a smaller jug, first add only half the amount of the fruit sauce with 1/2 liter of mineral water!