Fusion, a range of three fruit-flavoured beers, is currently being rolled out and Naked has been brought in to provide advice on aspects of the full launch, including Holsten's use of media and branding.
The appointment does not affect MediaVest's hold on the £6 million media buying account, with no review planned at this stage.
TBWA/London, the agency that created Holsten's, "who's the daddy?" commercials featuring Ray Winstone, is working on the advertising for the launch of Fusion. TBWA survived a review of the account two years ago.
Naked has been appointed by Holsten's marketing director, Andy Edge, after it supplied similar strategic advice to clients including ITV Digital, Sony PlayStation and Hutchison 3G.
Edge said: "Fusion will be hitting the shelves over the next two months. We have appointed Naked on a project basis because we wanted to take a look at the ways of bringing the Fusion brand into the market and the communications mix.
"Naked is working on total communications, not just media. It is creative and takes a clear view of the consumer. We are not excluding MediaVest, but taking a look at the whole consumer market."
Fusion is targeted at consumers in their 20s and will launch nationally throughout the coming weeks.
Edge said that promotions and sampling to support the brand would start in July with above-the-line activity in the final quarter.