The campaign backs an on-pack promotion and is part of a £12m brand relaunch that began in March with the introduction of four new flavours. It is the biggest SMS campaign run by P&G to date.
Kids who collect and send off eight on-pack labels will receive an exclusive S Club CD previewing a new track, Hey Kitty.
Fifty CDs will include VIP tickets to a Sunny D/S Club party in October, where winners will be able to meet the group.
The SMS campaign includes an exclusive message from the band. Participants are asked to text in a trigger word to receive a sound file; on hearing an introduction, users then have to opt in so that they can hear the complete message.
A follow-up text message will let recipients pass on the file to four friends by sending their names and mobile numbers.
James Pollock, assistant brand manager at Sunny Delight, said: "SMS is the ideal medium for communicating this exciting news, while remaining within our responsible marketing policies. It's the biggest SMS activity for P&G in the UK to date."
The campaign is supported by a web site (www.sunny-d.co.uk), where users can also apply for a 'virtual' drink label, find details of the CD and information about the VIP party.