He died at around age 33. Given the weak alcohol level of beverages back then (I believe? - no spirits back then) there must have been some other strong contributing factors.
He had just marched to the Indus and back, much of that through desert. He had around five serious wounds in his combats. He was very much in the front fighting. When he was laying up at Babylon there was a fever... Babylon was swampy in those days. Speculation is when he took ill he drank for medicinal reasons and inadvertently drank himself to death.