Most guys behave differently after consuming alcohol, and this often leads to situations in which a woman is left trying to decipher her crush's words or actions through the facade of its effects - not always an easy task, but as I will explain, not one worth completely abandoning either. Whenever a man you are interested in interacts with you (i.e. whether he is drunk or sober), he reveals information about himself, even if it is only that he is perpetuating the status quo of the relationship by not giving you any different information. A drunken interaction with a guy you like is no exception; you just need to understand the limitations of what you can learn from it.
Most people are familiar with the Latin expression "in vino veritas," which means "in wine lies the truth." There are a lot of dumb sayings out there, but this is not one of them. With a few negligible exceptions, a man's actions when he is drunk do accurately reflect his true feelings and intentions. This is because his drunkenness relieves his inhibitions, making him more capable of behaving according to his impulses and natural inclinations. However, from an attracted girl's perspective, this honesty carries with it an ambiguity, because in addition to relieving a man's internal inhibitions, alcohol also relieves his external inhibitions; and there is almost no way to judge which one is driving (or, more accurately, allowing) his words and actions. By internal inhibitions I mean those that come from within, i.e. ones that are a product of his personal weaknesses - fear of embarrassment or lack of self-confidence. By external inhibitions I mean those that come from the expectations of society, such as the pressure to date high-quality women, to not sleep with a girl you don't want to date, or avoid sleep sleeping with your female coworker for fear of upsetting your professional relationship at work. Both types go by the wayside when drunkenness sets in.
The loss of both of these types of inhibitions leave a man's natural impulses unchecked, and you can be sure he will start to act on them in proportion to his level of drunkenness. The ambiguity is introduced by the fact that a guy's sincere feelings might just as well be "I have a crush on that girl and want to date her," as they could be "I want to fuck that girl tonight and tonight only." In the light of drunkenness, however, the behavior resulting from both sets of feelings is one and the same: he flirts with you or gives you more attention. So the distinction between these two attitudes is not what you should be looking for when you try to interpret his drunken actions. You need to wait for a clearer data point to make this kind of judgement.
But as I suggested at the start of this post, this ambiguity does not mean no useful information can be gained from a guy's drunken advances. And this is because there is yet another external inhibition that is ignored by drunken men, namely, the concern that "I should be nice to this girl and talk to her even though I don't want to have sex with her or date her." Your clue comes entirely from his dismissal of this inhibition as he drinks. While you may not be able to determine whether or not his advances are purely sexual when he flirts with you, you can
at least rule out the possibility that he has no interest in you. If he weren't at least sexually interested, you can be sure he would be off chasing other girls, rather than being "tied down" by the social obligation to be nice, or even just social.
So next time the guy you likes makes a drunken advance, don't stress out trying to decipher the implications. Instead, acknowledge that it means he is at least sexually interested in you, and wait for your next (sober) data point.