I was watching a Youtube video of a man who supposedly drank 20 energy drinks in a row. It appears that his heart enlarged greatly. Is this something that energy drinks could actually do?
In short, there seems to be no evidence that acute caffeine overdose by drinking a great amount of energy drink would result in heart enlargement (hypertrophic or dilated cardiomyopathy). It could cause severe caffeine overdose, though.
8 oz (237 ml) of an energy drink can contain 150 mg of caffeine (Mayo Clinic).
20 such drinks would give you 3,000 mg (3 g) of caffeine and 4.7 liters of water.
3 g of caffeine, does not seem to be lethal:
Lethal doses of caffeine have been reported at blood concentrations of 80 to 100 micrograms/ml which can be reached with ingestion of approximately 10 grams or greater. (Stat Pearls, 2019)
4.7 liters of water drunk in a short time can result in fatal water intoxication. There is a report of a woman dying after drinking 4 liters of water in 2 hours.
Symptoms of caffeine overdose: How to recognize caffeine overdose (Nursing, 2019):
Moderate toxicity can cause restlessness, tremors, anxiety, mood changes, and gastrointestinal discomfort (such as vomiting). Very high doses of ingested caffeine (more than 6 mg/kg) can decrease both physical and cognitive performance and induce severe gastrointestinal distress. Extremely high blood levels (up to 150mg/kg) of caffeine can cause changes including hypokalemia, ventricular dysrhythmias, hypotension, rhabdomyolysis, and death. Blood caffeine concentrations around 150 mg/kg of body weight can be fatal.