The individual had been participating in the viral "75 Hard" fitness challenge, which involves drinking large amounts of water and following a strict diet and exercise regimen.

After drinking four litres of water over the course of 12 days, the individual began to feel unwell and was later diagnosed with a severe sodium deficiency.

The "75 Hard" challenge was created by YouTuber Andy Frisella in 2019 and has been described as an "Ironman for your brain." However, the challenge requires participants to drink a significant amount of water and follow a strict diet and exercise regimen, leading some to question its safety.

In the case of the TikToker in Canada, the individual was advised to consume less than half a liter of water per day in order to treat their sodium deficiency.

It is important to note that extreme physical challenges, such as the "75 Hard" challenge, can be dangerous and should be approached with caution.

If you are considering participating in a viral fitness challenge, it is important to consult with your physician or other healthcare professional to determine if it is right for you.

Additionally, it is important to listen to your body and seek medical attention if you experience any unusual symptoms or discomfort.