Mix still water, sugar, orange, lemon, mint leaves and vanilla pod in a small saucepan. Bring to a boil, then remove from the heat, add the tea bags and cool down for 5 mins.
Remove the tea bags and pour cup of the hot tea into a separate bowl. Add the tamarind paste to it, stir to dissolve, and then strain the mixture back into the rest of the tea. Let the tea cool down to room temperature, then refrigerate for 1 hr.
Before serving, add sparkling water to 300ml of the iced tea.
The tamarind iced tea can be kept refrigerated for 1 night.