In Seongsu, go to Daiso Seongsu 2-ga (106 Seongdeokjeong-gil) or Ttukseom

Station (6 Achasan-ro), 10am–10pm; easy to add to a café crawl. The replaceable foam bottle brush is ₩1,000 (14K orders), and the standing brush, ₩1,000, stands upright instead of hanging. Standing up, it drains and stays clean.