According to an article by Smithsonian Magazine: “Just a single 12-ounce bottle of beer can make you more attractive to the insects."
Researchers suspected this was because drinking increases the amount of ethanol excreted in sweat, or because it increases body temperature - two things that are attractive to the tiny pests.
But are mosquitos looking for a bump? According to an article by Popular Science, mosquitos can indeed get drunk. However, they are much more likely to become inebriated from drinking fermented fruit or flower juices than from sucking the blood of someone who has had a few too many.