Travelers crowd the departure hall at Incheon Airport on July 22 as the summer vacation season gets underway. (Yonhap) The first purchase many international travelers make in Korea is not a SIM card. It happens at a convenience store in the arrivals hall, and it usually involves a transit card and a plastic tub of banana milk.CU, a local convenience store chain, said the bestselling item at its nine stores near the arrivals area of Incheon Airport from January through Aug. 17 was the Tmoney Travel Card. Binggrae Banana Flavored Milk came second, followed by Lotte Icis bottled water, a Dubai-style chewy cookie and adapters for Korean outlets.The order flips on the way home. At CU's 10 stores near the departure gates, banana milk was the top seller.Across all CU branches at the airport, banana milk sales rose 43.1 percent from a year earlier. Some travelers have been seen arriving with cooler bags and buying it in bulk. Tmoney Travel Card sales rose 831.7 percent.Drinking the banana milk straight is no longer the whole appeal. Foreign visitors have moved on to building their own drinks with it, assembling the ingredients at the convenience store counter. The most common version is a banana milk latte, made by combining the milk with black coffee in an ice cup. The recipe has been circulating widely on social media.The Tmoney Travel Card, designed for short-term visitors, covers public transit nationwide and carries discounts at partner shops, cultural venues and attractions in Seoul, Gyeonggi Province and Busan. Its sales growth tracks the rise in independent travelers without a guided tour.The Dubai-style chewy cookie sitting on both lists was invented in Korea. Its filling was inspired by Dubai chocolate, the pistachio and kadayif bar that an Emirati chocolatier made famous online. The marshmallow shell around it is a local addition. The cookie set off a craze here over the winter.