What is the best-selling item in KTX trains?

A fun fact about train rides in Korea: The most sold item on KTX trains is banana milk since four years.

In the first half of this year banana milk was the best-selling item in the Korean bullet train. Around 264,000 banana milks were sold. Cass Beer is second (147,000 sold cans), water on the third rank (115,000 bottles) and Hite Beer is fourth (108,000 cans). This is Banana Milk (바나나우유):

Banana milk is the best-selling product in the KTX since 2010. The demand for banana milk is actually steady decreasing: 805,000 in 2012, 752,000 in 2013 and 661,000 in 2014. But other products are selling less over the years, too.

The product with the highest sales is none of the above. Sold only 76,000 times the most sales have been generated with dried squid. The sale amount was 410 million KRW.
It seems that the demographic of users is different in other Korean trains because there beer dominates over banana milk.

Source: Yonhap News