Can one drink a beer outside the Sukkah? Since it is alcohol, it may be different than a regular drink... But then again, it's not as chashuv as wine or scotch...
"And it is permitted to drink water and wine and eat fruit [even if he established himself on them- REMA's own opinion] outside of the Sukkah. And he who is stringent upon himself, and will not drink even water outside of the Sukkah, he is praised."
- Shulchan Aruch with Rema; 639:2
"Water and wine and to eat fruit - The reason is that eating even a lot of fruit in an established setting, is equivalent to merely eating grain product (pas) in a casual manner. The same law applies regarding meat, fish, and cheese, (and other types of food) in that they are considered like "fruit" according to the opinion of the Shulchan Aruch. (And he was not strict at the end except with a cooked food made of the 5 grains.) And that (leniency) which the REMA notes, "and even if he established himself on them" also applies to wine, as is proven by the Darkei Moshe. His reasoning is that wine is merely considered like eating fruit (how much more so regarding other drinks). Therefore, even their established consumption is not important enough. And know, that many Acharonim argue on this law (of the REMA) and their opinion is that if one drinks wine in an established manner, he is obligated to do so in a sukkah..."
"....However, it is proper and correct, to not drink (even mead or beer) in an established manner unless it is within a meal (obviously in a sukkah) ... etc."
- Mishnah Berurah 639:13
"It is permitted to drink any beverage, even wine, outside the sukkah, even if one drinks more than a revi’is. (But) One who is stringent with himself and drinks no beverage, even water, outside the sukkah is praiseworthy.
When does [the above leniency] apply? When one drinks in a casual manner. By contrast, one is required to enter a sukkah if he [intends to sit down] to drink wine or other beverages that one commonly sits down to drink, such as mead or beer in these countries, [even] when a meal is not [served]."
- Shulchan Aruch HaRav 639:12
Although the Biur Halachah, brings the Ritva (who says that merely drinking a revi'is of wine, is called "established" and therefore needs a sukkah); when we look at the later poskim quoted above, it seems that we only have an argument between the Rema and others, if one is allowed to drink wine (or mead and beer) outside the Sukkah in an established setting. The Mishnah Berurah and S.A. HaRav, both seem to agree that one may drink wine mead and beer to quench thirst outside the sukkah as long as it is not a fixed established drinking session.
The definition of fixed and established drinking according to the Ritva would be based on a minimum amount consumed (revi'is), while the definition according to later poskim would be spending time sitting down (perhaps with a group of drinking friends) in a relaxed manner for an official drinking event.
IIRC, the Meiri, holds that wine may be drunk outside of the sukkah.
(Those who wish to say that there is such a thing as establishing oneself over wine which needs a sukkah, bring their proof from the Mishnah in Sukkah 25a and the Braisa in 28b which seems to treat "drinking" as a separate action obligated in a sukkah. Those who do not hold that wine can establish such an obligation point to Brachos 36b which says that wine does not establish anything.)
Conclusion: Most opinions hold that merely drinking wine or beer does not require a sukkah. However, some opinions hold that drinking wine or beer in an established manner, will require a sukkah. Some of these opinions hold that beer is just as important as wine for the purpose of requiring a sukkah.
(For resolving the question of requiring a brachah of "Leshev BaSukkah" on such drinking, see further in the above sources for particular situations, or ask a new question, as such details go beyond the scope of the OP IMHO.)