I use Oral-B dental floss.

Homeplus had a buy-one-get-one-free offer last month or so. That makes it about 2,500 won per pack. It's so cheap, right? Buying during a sale really makes the price less of a burden. It turns out it's Oral-B dental floss, which is highly recommended by dentists. When I used it, it felt a bit like white twine, if that makes sense? It's really sturdy and durable. So, it doesn't separate into multiple strands in the middle, nor does it break.