The Umbrella singer is one of four celebrities who are taking part in the Tap Project – offering fans the chance to win a collection of bottled TAP water!
The other stars joining her are teen queen Selena Gomez, country superstar Taylor Swift and Entourage actor Adrian Grenier.
The project encourages fans to sign onto the UNICEF Tap website and donate $5 towards the cause.
Once fans donate they will be entered into a competition to win The Ultimate Deluxe Platinum Celebrity Tap Pack.
The Pack features four limited edition bottles of water from Gomez, Rihanna, Swift and Grenier.
Each celeb has their face featured on their own bottle with the word Tap also printed on it.
Every dollar from fans' entry fee helps UNICEF provide clean, safe water to a child in need for 40 days.
Fans wanting to donate and have a chance to win the celeb water can log on to www.uniceftapproject.org