Abstract: Some drink manufacturers do not report how much Caffeine is present in their products. This work was done for the estimation of caffeine in ten different brands of energy drinks available in the market with the help of Ultra-Violet spectroscopy. These result showed that the concentration of Caffeine is much higher than in the different brands of soft drinks. The highest concentration of Caffeine was found in Power Horse (0.754955 mg/mL), so it is strongest CNS (central nervous system) stimulant among all other analyzed energy drinks. The lowest concentration of Caffeine among investigated energy drinks was Big Apple (0.100901 mg/mL). So it is the weakest stimulant among all samples.