There's some validity to claims that Yeltsin imbibed too much alcohol during his tenure after his assumption of the presidency. Incidents like Yeltsin's August 1994 trip to Berlin where he seized a baton and tried to lead an orchestra led to the public perception that he was an alcoholic. Such behaviors were atypical for world leaders and became fodder for tabloids and rumors. A number of insiders have pointed to Alexander Korzhakov, a bodyguard and one of Yeltsin's confidants, as one of the enablers of Yeltsin's drinking. Yeltsin himself admitted in his post-retirement memoirs that he turned to drinking around 1993/4 as a means to cope with the increasing stress of the job. Very few commentators prior to this period saw Yeltsin imbibe more than his contemporaries. Yeltsin's health problems also contributed to the public image of his alcoholism as he had to suddenly cancel his appearances. These health issues meant that Yeltsin had to curtail his drinking during the latter half of his presidency.

So Yeltsin did drink alcohol for some of his term and at times did appear to be inebriated at public functions. Whether Yeltsin was a "raging alcoholic" is a more difficult question to answer. The issue is a highly politicized one as a lot of the evidence for the affirmative is highly circumstantial. The tabloid nature of a "world leader behaving badly" adds a sheen of scandal to it that can magnify Yeltsin's drinking into something more significant than it actually was.

Source

Colton, Timothy J. Yeltsin: A Life. New York: Basic Books, 2008.