Woe to the crown of pride, to the drunkards of Ephraim, whose glorious beauty is a fading flower, which are on the head of the fat valleys of them that are overcome with wine! Isaiah 28:1
"Drunkard" in this instance is used metaphorically, referring to one who is carried away with his own sense of power, pride, and glory. The Israelites had become drunk with power and false religious zeal, the Baal worship. In the East when people are carried away with their false pride and power we say, "they are drunken."
Ephraim was situated in one of the most fertile parts of Palestine (note: the fat valley). The land was graced with wheat fields and vineyards. Wine was abundant. Then again, the people boasted of their power and glory. They were the descendants of Ephraim, the second son of Joseph, whom Jacob had blessed, predicting that he would become a great people [Gen. 48:5-22]. Moreover, the name of Israel, the prince of God, was bestowed upon Ephraim and his descendants.
Therefore, Ephraim was the crown of the pride of Israel, but had defiled himself by worshiping pagan gods. Now he was wearing upon his head a shameful diadem. Ephraim had been unfaithful. He made alliances with pagan nations, and had utterly forsaken the Lord God of Israel and his everlasting covenant.
(Lamsa, George M. 1964. Old Testament Light. San Francisco: Harper Collins., pg 663)