dean describes sam as a happy drunk, which does generally seem to be true every time we see him any kind of intoxicated, so some thoughts about this.
stripping inhibitions is generally what gets sam to fuck. post stanford, at least. pre or mid stanford, he rarely drinks, and when he does its for social events like a halloween or christmas party. he almost never gets shitfaced despite working at a strip club for the majority of that time. on the road, he feels too busy to really take a moment for himself--which is why he tends to let loose more at bars, which implicitly creates a wedge of space (theyre usually not there for only leisure, or if they are, the leisure block is one dean is also okay with, so sam wont get yelled at or face massive consequences for choosing to have sex with someone). sam does cruise a little, frankly, and did so numerous times in the months dean was in hell... typically at bars. getting a few drinks in him typically makes him more comfortable with engaging with sex pre cage, though i dont think he likes taking hook ups to his hotel room often--he shares it w dean and finds it inappropriate or at very least bad manners--so they'll go to the bathroom and occasionally the impala (hey if dean can fuck in the impala so can sam okay).
giggly, touchy, blushy, flirty, funny drunk. sam will almost always say what hes thinking for real if drunk.
surprisingly light weight for his height. however, sam is very good at pretending he's sober when he's tipsy or any level of intoxicated; it's only when he's really drunk that he cannot hide it. this is part of the hustling he pulled with dean: he couldn't just NOT drink while playing pool against chumps they intended to hustle, so he had to learn how to handle it.
his relationship with alcohol is mostly healthy. it is not the first thing sam turns to when upset and generally only comes out as a comforting tool when his brother is waylaid or dead.
has never willingly engaged with hard drugs. any dalliance sam has ever had with anything beyond literal demon blood was incidental or accidental. he has been roofied before and drugged by plenty of monsters and humans alike, and he has done like.. a single bump of blow at the club as a dancer (and didnt like it). never done any kind of other stimulants or hard drugs, has probably smoked weed before but not habitually. he mostly kept his nose out of drugs so he would always have a clear head for work and school, as sam strongly dislikes being in an altered state of mind for the most part.
his natal demon blood / what makes him somewhat inhuman from azazel makes his body interact with substances a little differently. i think some things metabolize harder and faster, and others, far softer and lesser.
demon blood is by far the "hardest" drug sam has ever done. (i do want to remind you all that sam was manipulated into using, since this is something a lot of.. certain kinds of spn fans like to hold against him as him being evil or what have you.. when its an addiction to a substance he never even willingly pursued on his own.)