Yes, sodium benzoate is a preservative. Sodium benzoate is a preservative for oral liquid drugs, which has the functions of preventing deterioration and souring and prolonging the shelf life. Excessive use will damage the liver and even cause cancer.

Red Bull Ingredients List:

Water, sugar, essence, taurine, lysine, inositol, vitamin B6, vitamin B 12, food additives (citric acid, sodium citrate, caffeine, sodium benzoate, lemon yellow, carmine).