In a large bowl, stir together the carrots, lemon and orange juice and sugar. Cover and let sit in the fridge for at least 1 hour (better longer) and stir occasionally so that the sugar dissolves. Then let the lemonade base run through a sieve and pour into a jug. The residues can be used in baking, e.g., in a carrot cake.
To prepare the lemonade, add 25 - 50 ml of base per glass, add ice cubes as you wish and fill up with 200 ml of sparkling water.