MARGARET I always thought drinkin' men lost their looks, but I was plainly mistaken. (I.29.316-317)
The fact that Brick does keep his looks is quite remarkable considering the amount he drinks. It's almost as though Fate is playing a cruel trick on him by allowing him to keep the appearance of normalcy, while destroying his internal self. He still remains attached to society through his looks, but the alcohol eats away at his insides.
BRICK It just hasn't happened yet, Maggie. MARGARET What? BRICK The click I get in my head when I've had enough of this stuff to make me peaceful….(I.33.702-705)
Without alcohol, a war wages within Brick as he deals with the lies in which he's been complicit. Alcohol helps numb the lies.
MARGARET […] My daddy loved his liquor, he fell in love with his liquor the way you've fallen in love with Echo Spring! […] (I.54.886-888)
Maggie is surrounded by alcoholics, men who turn to alcohol to fill the gaps in their lives and to help themselves battle them battle bitter truths. She never drinks throughout the play, but she also says that she never trusts a man who doesn't drink.
From then on Skipper was nothing at all but a receptacle for liquor and drugs….(I.59,1135-1136)
After Maggie confronts Skipper about his love of Brick, he gradually kills himself through alcohol and drugs. The truth kills him.
BIG DADDY Where you goin'? BRICK I'm takin' a little short trip to Echo Spring. (II.88.600-601)
Brick likens getting drunk to traveling. He is traveling away from reality. The way in which Brick specifies that his trip will be short reminds us that there will be a return and makes us think of the alternative, much longer trip: death. In this way, Brick drinks to approach the peacefulness of death.
BIG DADDY A whiskey highball would injure this spastic condition? BRICK No, sir, it might do it good. (II.92.664-665)
While we know that alcohol is probably the last thing Big Daddy should be drinking, in this moment, with Big Daddy cradled in the lie of his spastic colon, alcohol becomes medicinal and connects the father and son.
BRICK - I'd better sit by myself till I hear that click in my head, it's just a mechanical thing but it don't happen except when I'm alone or talking to no one…. (II.99.824-826)
Brick describes his click of peacefulness as "just a mechanical thing," showing us that he knows this peacefulness to be fake and temporary. He must withdraw from the world in order to hear it, because being around others will only remind him further of the lies from which he's running.
BIG DADDY If I give you a drink, will you tell me what it is you're disgusted with, Brick? (II.106.958-959)
Alcohol becomes a kind of currency in the play. Both Maggie and Big Daddy want something specific from Brick, and the only way to secure what they want is to take control of the thing he desires most of all. In this way, alcohol is a tool of power.
BIG DADDY Is liquor the only thing that'll kill disgust? BRICK Now, Yeas. BIG DADDY But not once, huh? BRICK Not when I was still young an' believing. A drinking man's someone who wants to forget he isn't still young an' believing. (II.112..1082-1086)
Brick hasn't always needed to drink. He drinks now to quell the realization that he is no longer the beloved football hero. He drinks because he's lost his belief in life. It seems like the only things that the characters in Cat believe in are everlasting life and wealth. Once Brick sees he's lost the qualities that once formed the core of his identity, he no longer has a steady foundation to rest upon should he kill the mendacity in his life. Brick's identity was and is so dependent upon what others believe him to be; this is the cause of his drinking.
Anyhow now!—we have tracked down the lie with which you're disgusted and which you are drinking to kill your disgust with, Brick. […] This disgust with mendacity is disgust with yourself. (II.124.1366-1369)
Is Brick really trying to kill his disgust by drinking, though? He seems to be simply numbing his disgust. If we follow Big Daddy's logic here, Brick's drinking habit takes a masochistic turn. He drinks both to quell his warring mind and to punish himself for the lies he's fueled and sustained.