The first time* I ever heard of and tasted boiled coke with ginger and lemon was two months ago during breakfast at Tai Hing, a roast pork/diner chain in Hong Kong. My initial reaction: "...Boiled Coke? What the?" And then a second later: "I MUST TRY IT RIGHT NOW."
Boiled Coke with ginger and lemon started off as a popular cold remedy in Hong Kong, but now it's a popular anytime drink that's found at pretty much all Hong Kong diners. As a first-time, not sick drinker, I found it surprisingly pleasant. The cold and fizzy are gone, but you're left with sweet, spicy, a little tart, a smidge medicinal—all things that would feel restorative on a cold day or in a stream of warmth going down a sore throat.
I made a batch at Serious Eats HQ for the rest of the office to taste. Everyone was skeptical but liked it more than they expected to. Or at least they thought it would be nice to drink while sick, not so much to drink for fun.
If you've never had boiled Coke with ginger and lemon, try making it at home. The name is pretty self-explanatory, but I wrote up a recipe anyway. If you have other favorite hot soda drinks, do share.
I'll point out that former Serious Eats intern Michele Humes mentioned this drink on Serious Eats back in 2009. I apparently hadn't read that post. Oops.