High doses of caffeine can cause jitters, nervousness, insomnia, headaches, and nausea – all things nobody wants to deal with during their day-to-day life.
Additionally, if consumed in large amounts over time, studies have linked high levels of caffeine intake to long-term cardiovascular problems such as hypertension and arrhythmia.
Another potential problem with consuming C4 is that it contains artificial sweeteners like sucralose and acesulfame potassium (ACE). Studies have suggested links between these substances and various health risks, including diabetes and obesity.
Plus, they don't provide any nutritional benefit – meaning that all those empty calories could add up quickly without providing anything beneficial in return.