I'm a dentist and that's why you should never let your toddler drink from your trendy Stanley cup

Everyone from Adele to Meghan Markle is a fan of the Stanley Cup, the viral £45 water bottle that has become extremely popular with Gen Z.

But now new mums are giving the super-sized, 850ml insulated water cup to their babies, prompting a dire warning from dentists.

Dr. Sachin Soni, owner of Lady Bay Dental Care in Nottingham, warned that drinking from a straw can be harmful to young teeth.

'If a mother or father came along and asked if it was okay or not I would say try to avoid it in young children as it can negatively impact tooth position and growth of the developing jaw' , he told FEMAIL.

'CChildren who use a straw too often can sometimes cause changes in tooth position while the jaw is still developing.

'We advise parents to limit the frequency of straw use, usually young children between 1 and 3 years of age.'

But that hasn't stopped dozens of mothers from sharing clips of their babies enjoying drinking from the giant cup, which has become a viral sensation.

While the colossal tumblers come from a variety of makers, such as brands like Yeti (Victoria Beckham's favorite model) or Simple Modern (Meghan's favorite), the current king of water bottles is the Stanley 'Quencher'.

The hashtag #Stanleycup now has more than seven billion views on TikTok and a cult-like following online, with celebrities like actress Shay Mitchell and Love Islander Molly Mae Haag evangelizing about it. They come in dozens of different colors, all of which sell out within minutes of release.

In the US, hordes of customers queued outside a Target store overnight for a deal on the limited-edition cup, with men even queuing to buy them for their young daughters – and now mums are letting their children have their swap milk bottles for the giant accessory.

Now that the trend has crossed the Atlantic, flasks at John Lewis are selling out quickly.

And it's not just babies who need to be careful about protecting their teeth.

Trends like water tok, where young people flavor their water, have undoubtedly helped accelerate the Stanley craze.

Millions of Gen Z women were inspired to make funky water by adding kitchen cupboard staples like chia seeds and lemon and flavor sachets.

While adding colorful agents to your water can make it more palatable if you're not a natural H2O lover, this may be tempting, but dentists recommend the opposite.

'Beverages with high sugar content increase the risk of tooth decay, acid erosion and sensitivity,' says Dr Sachin Soni.

But this hasn't deterred fans from the craze.

Primark and The Range will create dupes at a much lower price point of £8 and £4 respectively to keep up with the trend.

But what's so special about the Stanley, which was first made in 1913?

The all-steel thermos was invented by physicist William Stanley Jr. because he wanted to “keep his coffee hot all day.”

It became popular for its portability and ability to reliably store drinks for hours without leakage.

Just last week, Stanley sent social media into overdrive with a highly anticipated limited-edition collaboration with Starbucks for Valentine's Day.

Videos emerged of shoppers in America queuing overnight to get their hands on the brightly colored pink and red cups worth £35. Viral footage even showed a man trying to grab a box of it before being tackled and beaten up by other customers who had been queuing for hours. The cups are now selling for as much as £150 each on eBay.

So how did an insulated cup – which, let's face it, once reserved for construction workers and mountain climbers – become the ultimate fashion statement?

Since William Stanley Jr – not of the Stanley knife – invented the steel vacuum flask in 1913, the Seattle company has sold a variety of cups – from 14 oz (400 ml) to 64 oz (1.8 L), suitable for long-haul drivers, road trip workers, picnickers, hikers and more.

World War II pilots carried Stanleys on their planes. As recently as 2012, Stanley said its products particularly resonated with “an experienced police officer with a 30-year career” and “a retired Army soldier.” It's safe to say that Stanley fever didn't happen overnight.

It wasn't until 2016, when the company released their Quencher model, that the brand captured the imagination of Generation Z, born between the late 1990s and 2010s.

On TikTok, influencers started sharing how much water they had in their cup and how it kept them “hydrated.” Pop queen and TikTok royalty Olivia Rodrigo created a new wave of devotees last year.

“I was actually influenced by TikTok to buy this,” Rodrigo said, cradling her lilac cup in a video interview with GQ.

“I thought, 'I need this. This looks like it's going to change my life.' And that was absolutely right.'

Stanley's revenue has soared, from $94 million in 2020 to $194 million in 2021, and doubled again to $402 million in 2022.

Ostensibly, it is the usability of the product that appeals. At the heart of the Stanley Tumbler's popularity is its insulation technology which, as I can testify, really does keep drinks hot or cold for up to 24 hours.

In November last year, TikTok user Danielle Marie Lettering proved this point to the hilt. She posted a video of her car catching fire. Amid the charred debris of her burned-out Kia, her copper-colored Stanley sat completely intact in the cup holder on the driver's seat, the ice still frozen in the cup. The video now has more than 94 million views. The company was clearly excited about the marketing opportunity and when Stanley saw the video, the company offered to replace not only the cup, but her car as well.