When Odysseus goes to inspect the cave that he later learns belongs to the Cyclops, Polyphemus, he brings with him a goat skin bottle of dark wine that was given to him by Maron, a priest of Apollo, who watches over Ismarus (the first stop Odysseus and his men had made after leaving Troy). Maron gave him this wine and many other gifts in gratitude that Odysseus had protected him and his family. 

Odysseus explains to Alcinous that this wine is incredibly strong: when Maron would prepare it to drink, he would mix one part of the wine with twenty parts water. It is important to note that ancient Greek wine was different from the wine we have today. It was very thick and strong, and they would mix it with water to make varying strengths depending on what they wanted for the occasion. Odysseus says that, even mixed at the ratio of 20:1, the wine was still quite strong. He brought it along with him, he explains, because his "'stout heart suspected [he] soon should meet a man arrayed in mighty power, a savage, ignorant of rights and laws.'" Therefore, he claims, he took the wine (and some other provisions) with him because he had some intuition that it would come in handy, and it really did!