Clean the rhubarb and cut into pieces. Peel the ginger and cut into slices. Bring the rhubarb to the boil with sugar, ginger and 1 liter of water in a saucepan.
Add the tea bags and cover everything over a low heat for about 8 to 10 minutes. Let the rhubarb juice cool down and then pour it through a fine sieve. Pour crushed ice into glasses and top up with the rhubarb juice.