FATwater is a type of purified water, infused with a fatty oil found in coconuts.
It's the latest health drink to come from the creator of Bulletproof Coffee, David Asprey, who came up with the idea of adding butter to coffee to give you an energy kick.
Fat water comprises three ingredients: XCT Oil ("a prized fat source from coconuts"), purified water and natural flavouring.
The water, which is available in a variety of flavours such as berry, orange and lemon, contains less than 30 calories and zero sugar. It's also supposedly great for hydrating the body and boosting energy levels.
For those concerned about weight gain, founder David Asprey told the New York Daily News that the water doesn't have that effect.
"The oils enhance thermogenesis, which is a fancy word for ‘fat burning'," he said.
"They get burned as energy and have an appetite-suppression effect. It’s not like we put in sunflower oil or canola."
The drink is currently only available in America and costs $3.95 a bottle, however - much like Bulletproof Coffee - it'll probably soon make its way over to the UK.
But despite it already being sold out on the Bulletproof website, not everyone is convinced by FATwater.
Charlotte Stirling-Reed, registered nutritionist and owner of SR Nutrition, believes there's "little need" for this kind of product as we can already, quite easily, consume fat through other channels.
"In the UK we are currently in the middle of an obesity epidemic - another reason why this product placement seems a little strange - and fresh tap water is perfectly healthy for hydrating our bodies," says Stirling-Reed.
"For those who want a little more, coconut water is also fine to drink but one of my healthy eating rules is to limit the amount of calories you take in in liquid form, so I personally would not opt for or recommend FATwater."
Food is our ultimate fuel, she says, for energy.
"Opting for wholemeal carbohydrates and grains such as quinoa, buckwheat and oats as well as protein-rich nuts, seeds and natural yoghurt will give you a long lasting energy boost.
"Plus they contain plenty of fibre to keep you fuller for longer too."
Meanwhile Jo Travers from The London Nutritionist says there are "nicer ways to boost your fat intake than by drinking fatty water" such as eating coconut or cheese.
"It seems bizarre to me to make something like this when you could get fat along with other nutrients in actual food that is enjoyable to eat," she adds.
"A good way to boost energy is to have five fist-sized portions of slow-release carbs spread throughout the day.
"Also make sure you are properly hydrated (fat-free water is fine for this); and that you are getting enough iron. This is particularly important for women, as they need double that of men."
In terms of taste, New York Daily News reporters who trialled the water say the berry flavoured version tastes like "liquid soap".
The jury's out.
