Mix half a tablespoon of lemon juice and a pinch of salt with ginger slices and keep aside.
Peel the banana and cut it into 1-inch pieces. Mix with half a teaspoon of lemon juice and keep aside.
In a bowl, combine potatoes, sweet potatoes, and banana pieces. Add the remaining lemon juice, tamarind pulp, green chilies, chaat masala, salt, and coriander leaves. Mix well.