The article you linked was really good it discusses how caffeine, including drinks like Celsius, can contribute to brain fog and fatigue the article highlights the Euphoria you feel when you drink caffeine and how It gives an initial boost in energy and focus, but it has many negative side effects like shakes, headaches, fatigue, migraines, etc. But one thing to also consider besides the caffeine aspect of it is how much other additives are in Celsius and how that also affects the brain