Instead, the pair found the syrup-based drink made by GlaxoSmithKline (GSK) contained almost no trace of vitamin C, and one commercial orange juice brand contained almost four times more.
GSK had paid little attention to the claims of Devathasan and Suo until their complaints reached the New Zealand's consumer watchdog Commerce Commission.
But appearing in an Auckland court on 15 charges of breaching the New Zealand's Fair Trading Act, GSK pleaded guilty and admitted its ads may have left consumers with a wrong impression of the health benefits of Ribena.
The judge fined the company a total NZ$227,500 ($163,700) for misleading advertising.
The Commerce Commission said GSK's behavior was a "massive" breach of trust with the New Zealand public.
"As a multinational company specializing in pharmaceuticals and health products, they should have had robust testing and quality assurance systems in place to ensure its product was delivering what it promised," Commission chair Paula Rebstock said in a statement.
GSK told the court it had not deliberately set out to mislead consumers, and the fault lay with its testing methods.
"The fact that some of our products had incorrect labeling is to us, unacceptable, and we sincerely regret any confusion caused to customers who feel they may have been misled," GSK said in a statement.
The court also ordered the company to place advertisements in major metropolitan New Zealand newspapers to correct its mistakes.
Ribena, first made in the 1930s and distributed to British children during World War Two, is now sold in 22 countries.
Take that lovers of that sick drink! Lol! I did not make this story up and it's in todays 'Straits Times' and todays 'Today' for those who would want to read more. According to those newspapers, Singapore is testing the drink right now and I guess we'll be hearing about it on 'News 5 tonight' soon. And you wonder why you got sick so often even after drinking loads of Ribena.