Heat 500ml water until boiling.
Pour hot water over butterfly pea tea flower until it the water turns blue. Set aside until cool and freeze over night on ice cube tray.
Boil 250ml water with rosella tea flower for 5 minutes. Set aside until cool.
Crush frozen Sprite and frozen butterfly pea tea with blender. Set aside.
Squeeze lemon. Set aside.
First put rosella tea into a glass about 1/5 of the glass height, then crushed frozen sprite (1/3 of the glass height), crushed frozen butterfly pea tea (1/3 of the glass height), 1 tbsp lemon juice, 100ml cold sprite, and crushed frozen butterfly pea tea (until the glass is full) sequentially.
Repeat for 3 glasses.