Short verdict
Buy in Korea. Best purchased during a Korea trip, usually because of local access, price, testing, or limited bundles.
Instant coffee sticks can be a sensible Korea buy because they are small, sealed, and easy to share.
What to know
Buy in Korea if you want to compare flavors and pick up compact boxes from marts or convenience stores.
What to avoid
Buy online if you already know the flavor and can get a fair price from a trusted marketplace seller.
Final verdict: buy in Korea for discovery, online for reorders.