Busan drinks outdoors far more than Seoul does: the night is built around the beachfronts at Gwangalli and Haeundae, with Seomyeon as the dense inland district that stays up latest.
Gwangalli Beach
The beachfront strip faces the lit Gwangan Bridge and is lined with bars, cafes and convenience stores people drink outside. Metro Line 2 to Gwangan, then about ten minutes on foot; the city also runs a drone light show over the water on scheduled evenings.
Seomyeon
The largest concentration of bars, tented pojangmacha and noraebang in the city, around Seomyeon station where Metro Lines 1 and 2 cross. Loud, late and overwhelmingly a local crowd rather than a tourist one.
Kyungsung University area
Student bar quarter around Kyungsung University–Pukyong National University station on Line 2, with the cheapest drinks in the city and a scattering of small live-music and craft-beer places. Noticeably quiet during university holidays.
The Bay 101
Marina complex at the Haeundae end of Marine City, best known for the night view of the towers reflected in the water. Bars and restaurants on site, and plenty of people simply stand outside with a takeaway drink; walking around costs nothing.
Galmegi Brewing
Busan's own craft brewery, running taprooms in several districts of the city. Locations and hours have changed over the years, so confirm which branch is open before setting out.