Diet Pepsi sales have continued to plunge as customers complain that replacing controversial sweetener aspartame has ruined the taste of the drink.
While the firm say the new sweetener was approved by three quarters of customers in tests, Pepsi purists have complained that the new soda is too sugary and is putting them off.
David Zimdars, from Ann Arbor, Michigan, has been drinking diet Pepsi for 30 years and claims to have a two-month stockpile of the old recipe drink at his house.
Speaking to Yahoo Finance, he said: 'It has a nasty aftertaste, and it’s sickly sweet. You have to wash it out with water.'
Worse still for Pepsi, Zimdras says he plans to break with the habit of a lifetime and swap to diet Coke when his stash runs out.
That view reflects a pronounced fall in sales for Pepsi, which has seen it outpace a decade-long decline across the sector as customers give up soda in favor of healthier alternatives.
All of PepsiCo’s diet soda sales fell 6.6 per cent in the U.S. in the four weeks ended Sept. 19, as the new Diet Pepsi was rolling out nationwide.
That was worse than the 5.7% decline over the previous 52 weeks, according to Morgan Stanley, and than the 3.4% drop in diet soda sales at Coca-Cola, which hasn't replaced aspartame.
Pepsi chose sucralose, commonly known as Splenda, to replace aspartame, which has been dogged by intensifying concerns over its safety in recent years.
The new recipe has also been attacked online, with the most common terms used being 'yucky' and 'unpalatable', according to research.
Diet Pepsi sales fell by 6.6 per cent last month as customers complained that a change in the recipe had ruined the taste
PepsiCo's diet drink sales fell after they replaced controversial sweetner aspartame with sucralose, and fell faster than Diet Coke sales, which has not removed the chemical
Negative remarks outweigh positive ones by a factor of 6-1, and while internet users are famous complainers, the typical ratio is 4-1, meaning Pepsi appears to have got something badly wrong.
Rick Miller, a vice president at social media tracker Networked Insights, said: 'The early verdict on Diet Pepsi does not look promising.'
PepsiCo says it is rolling out thousands of National Football League-themed advertising displays in stores featuring Diet Pepsi and is ramping up free 'sip samples' across the country.
It has also shipped the new version to celebrity athletes and musicians in the hopes of endorsement.
PepsiCo Chief Executive Indra Nooyi added: 'Our belief is that you’ve got to wait a few cycles to see what the purchase repeat adoption cycle is.'