Schmoo will be sold in the luxury London store in January and the firm, set up by Hayley Hadfield and Laurence Nair-Price, has increased its listing in Tesco to 160 stores this year.
The pair launched their version of the Indian yoghurt drink – popular in curry houses as it cools the palate – in 2007, after graduating from Leeds University.
The Harrods move comes as they look to grow Chroma Life, their other venture which produces art for hotels, in the run-up to the London Olympics in 2012.
Miss Hadfield, whose father came to Britain from Pakistan when he was 14, and Mr Nair-Price, whose father is from India, won the deal with Harrods after an impromptu visit to the store.
Mr Nair-Price walked in and asked to speak a buyer. He had no luck initially but, after returning the next day, convinced the Knightsbridge store he was serious. After providing information on Schmoo's supply chain, the firm's application was accepted and the drink will sell for one month initially, which Mr Nair-Price and Miss Hadfield hope to extend, and will be displayed next to the Indian food.
An "exclusivity" agreement means it will not be sold in Harrods's main rivals. The product, which uses only four ingredients, will be aimed at first-time buyers and tourists but Mr Nair-Price and Miss Hadfield said they could not put a value on the deal.
They also plan to launch a Tetra Pak version of the drink in February or March – easier to export because it has a longer shelf life – after working with UK Trade & Investment. They have already met the Icelandic ambassador to Britain and plan to launch there and in mainland Europe.
"Getting into Iceland is quite easy because we didn't need to change the packaging," Mr Nair-Price said. Schmoo was renamed from yalp – "play" spelt backwards – earlier this year, in order to appeal to its core market after the firm's work with a branding agency. It has also had spells on sale in Morrisons stores.
The drink is made entirely from natural ingredients, including fresh yoghurt, and is based on a traditional Indian recipe known to aid digestion. Miss Hadfield and Mr Nair-Price began with a mango flavour and have since added vanilla and strawberry. The drink is selling between 3,000 and 4,000 units a week.
The other business run by Mr Nair-Price, who lives in Sheffield, and Miss Hadfield, who lives in Linton in Wetherby, is set to grow next year as London hotels carry out refurbishments before the Olympics.
The firm, which provides artwork, mirrors and accessories for the hospitality industry, commissions art and then buys the right to use it under a digital licensing agreement. It works with about 30 artists, with the two entrepreneurs visiting properties before deciding with the managers what would best hang on the walls.
They have worked with hotel groups including Marriott and Thistle. Chroma Life will turn over around 300,000 in the 12 months to April 2011 and its owners hope to take this to between 800,000 and 1m in the following year.