Energy drinks contain stimulants like caffeine, taurine, guarana, and B vitamins that affect the central nervous system and provide effects like increased alertness and motivation. Most energy drink ingredients are synthesized in a lab rather than being naturally derived, with the exceptions of ginseng, ginkgo biloba, and guarana seeds. Energy drinks are produced by combining these ingredients into a simple syrup base and then adding carbonated water. While energy drinks can increase alertness, their long term safety is uncertain as high caffeine intake has been linked to health issues like irregular sleep and heart problems if consumed in excess on a daily basis.