Sweden used to have its own version of Irish Coffee: kaffekask. It was big in the 19th century and I believe it dropped from favour during our 1917-55 period of liquor rationing. Nobody seems to drink kaffekask anymore.
A kask is a type of helmet like the ones worn by English bobbies. But that’s apparently not the etymology of kaffekask. More likely it comes from Low German karsch, “harsh”, “abrasive”.
Kaffekask consists only of coffee and 40% (70° proof) potato schnapps plus optionally a sugar cube per cup. Swedish schnapps (brännvin, “burn wine”) is usually flavoured and does not to my knowledge go through the barbarous vodka process where you distill nearly pure alcohol and mix it down again with water. But that is not to say that it is anything like Irish whiskey. Brännvin nowadays is an old folks’ drink taken only at a few ritualised feasts a year to the tune of old drinking songs.
Should you still want to try this blast from the past, there is a traditional way to get the proportions right. You put a silver coin and a copper coin in your cup. Pour coffee into it until you can’t see the silver coin anymore. Then top up with brännvin until you can see the copper coin again. It will be harsh.