1. Collect hibiscus (Sembaruthi) flowers and take the petals alone.
2. Wash them clean and soak them in 1/2 a litre of hot water overnight.
3. Strain them and remove the petals from the water.
4. Now the water would have turned red.
5. Take the water in a pan and add sugar to it.
6. Boil until the sugar dissolves and bubbles well.
7. Remove from flame and add juice of one lemon and mix well.
8. The squash would be really red enough.
9. So you need not add any extra food colour to it.
10. Hibiscus squash is ready to use.
11. Add 1/3 glass of squash and mix in plain soda or water to it and serve chilled.
12. You can store the hibiscus squash in a refrigerator for 6 months.

Recipe courtesy: 4th sense cooking