The start-up Rudaizky-Ryan, which was formed by the former Saatchi & Saatchi managing partner John Rudaizky and the former Spectre director Matt Ryan, won the £4 million business from the incumbent, Burkitt DDB.
Manning Gottlieb will handle all media buying and planning on the account.
T&T's owner, the independent soft drink company T&T Beverages, said it had been impressed with Rudaizky-Ryan's through-the-line approach to the brief. The company has also appointed the branding specialist Form to redesign the product's packaging.
Last year, T&T sponsored the British film Ali G Indahouse, as well as ITV's successful Pop Stars programme. It declined the sponsorship of the follow-up, Pop Stars: The Rivals, preferring to concentrate on developing a new brand strategy.
In addition to the rebranding, the T&T drink has been revamped to contain no added sugar, and the company was keen to launch a new advertising strategy to mark the product changes. The new campaign is expected to begin next month and will feature television advertising.
Rudaizky said: "The T&T team has huge ambitions and know that advertising alone will not be the answer. It was an ideal brief for our new operation and we are obviously thrilled to have secured the business."
Dafer Alazri, the managing director of T&T Beverages, added: "We have made significant improvements to the T&T product offering, and were looking to appoint an agency that could deliver a fresh marketing approach."