The #watertok trend has amassed close to 96 million views on the app.

Creators use sugar-free packet flavourings, protein shakes or coffee syrup to flavour their water. For many of us, it is not a far-cry from the ubiquitous cordial of our youth.

Many TikTokkers speak about the 'benefits' of their new water intake although none appear to list specifically what those benefits are.

University of Sydney's Dr Nicholas Fuller researches weight loss and is a program leader at the Charles Perkins Institute. He said the flavourings were a "fad".

The trend is also expensive. Flavouring brands have been quick to sponsor influencers and many creators encourage their followers to buy high-end class cups, specialty water boxes or even custom ice machines.

"You certainly don't need those things when you're drinking water," Dr Perkins said.

"When you're trying to increase your water intake, the best way to do it is with natural ingredients like infused lemon, lime or herbal tea."

"When water has anything added, like sugars and flavours and colourings, it's generally going to be a gimmick," he said.

But #watertok appears to be a gimmick that sells. Videos descriptions often include the hashtag #skinnymixes which appears to be an undisclosed ad for a brand of flavouring.

Skinny Mixes branding is all about enjoying food and drink 'guilt free' with a focus on healthy living and weight loss. Almost no nutritional advice is provided on the company's website.

Dr Fuller said trends marketed for weight loss could be harmful and lead to disordered eating especially for those who have tried weight loss techniques.

"It is important that people aren't following this for weight loss or diet reasons," he said.

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"It is certainly not something you should be doing to try and lose weight."

"Flavoured water should not replace food in a person's diet," Dr Perkins said.

"If you were following this sort of fad long-term, it can lead to an unhealthy relationship with food."

Many Australian creators have taken comedic digs, including @steph_who___, who parodied the trend with Cottees cordial.