The actor will be featured in all communication and promotional campaigns of the brand.
A new commercial has been shot with Genelia, which has been directed by ace ad film-maker Prahlad Kakkar and is slated to go on air from March.
Genelia will be seen in the advertisement with six-year-old Avan Khambatta.
Rasna's Chairman and Managing Director and Ayan's father Piruz Khambatta said; "Genelia's charisma resonates perfectly with our brand's full of life attribute. Youth relate with her girl next door image which will help us to reach the young generation in a fun and effectual way.
"She is the perfect choice for being a face for Rasna. We are confident to create a rage around the same in the market when the vibrant actress and endearing Avan will come together taking a cool Rasna sip. I am proud to welcome Genelia in the Rasna family and Avan for her first commercial feature."
In the past, Rasna has roped in celebrities like Karisma Kapoor, Hrithik Roshan, Anupam Kher, Paresh Rawal and Kapil Dev.