This recipe is part of our street food menu.
Bring 4 cups water to a boil in a medium pot. Add tamarind, reduce heat to medium-low, cover, and simmer 15 minutes; halfway through, stir tamarind to break it up. Arrange a fine sieve over a large bowl. Working in batches, use the back of a wooden spoon or ladle to press tamarind liquid through the sieve; discard solids that remain. (You should have 2 1/2 to 3 cups tamarind puree.) Transfer puree to a large pitcher; stir in salt and 5 cups water to make a tea.
Meanwhile, in a small saucepan over medium-high heat, place ginger, sugar, and 1 cup water; bring to a boil. Reduce heat to medium-low, cover, and simmer until ginger is softened and syrup is very fragrant, about 25 minutes; discard ginger slices and let syrup cool.
To assemble coolers: For each, pour about 1 cup tamarind tea and 3 tablespoons ginger syrup into a tall glass filled with ice cubes; top with 1/4 to 1/2 cup club soda.