The Gerber Juice Company, SunnyD's UK distributor, appointed the agency without a pitch. My Agency already works with Gerber on Welch's Grape Juice.
The £4.5 million summer campaign will push the product's healthier credentials and will include TV, press, radio, DM and digital elements. It comes after extensive moves to rid the product of its artificial flavours and make it more appealing to parents.
Sunny Delight was launched in the UK by Procter & Gamble in 1998 and it became the third-biggest soft drink in the country.
However, sales slumped after it came under heavy fire from anti-obesity lobbies and its "day-glo" orange colour became synonymous with preservatives and colours.
In 2004, the brand was sold to The Sunny Delight Beverages Company, which has since removed all the artificial preservatives, flavourings and added sugar.