Place the chiles, garlic, beer, water and salt into a large Dutch oven and stir to combine.
Place the pork in the mixture and bring to a boil.
Once boiling, lower the heat, cover and bring to a simmer. Cook for 60 to 80 minutes (or until pork is able to be easily pierced with a fork) and stir occasionally.
Uncover and continue to cook for about 45 to 60 minutes, stirring occasionally to prevent burning. Once most of the liquid is absorbed and the carnitas are browned and falling apart, the carnitas are done. Serve with a dollop of sour cream, chopped cilantro and a squeeze of lime juice. Oven-roasted corn on the cob (see notes for recipe) with cilantro-lime butter (see notes for recipe), black bean puree (see notes for recipe), rice or corn tortillas are all excellent options to serve with this dish.