Nothing sweet! When I still made moonshine, I would have my still set up so the product would go through six layers of charcoal and coffee filters as it dripped into a funnel going to the jugs. It had the same effect as aging it for a long time. The best flavor I ever made was with a braid of sweet grass put in the gallon jugs. Delicious, subtle, and no hangover like sweet concoctions will cause!
With all that filtering you're making vodka not whisky. Nothing wrong with that but it's not really whisky. That's why there's negligible hang-over. It's a two headed coin. The flavour but also the hang-over (if you drink a lot) comes from the impurities.
The flavour is contained in the impurities. When you distill, you discard the foreshots but set aside the "heads" (the acetone-like aromatic high-proof alcohols) then collect the "hearts" (main part of the run with the sweet tasting alcohol) eventually the proof drops to the point where the "tails" starts (wet hair of the dog smell). Those are set aside too. The proportion of heads and tails added to the main run determines the flavour profile. A big distillery doesn't set aside heads & hearts but rather the experienced still master knows the right points in the run to "throw the switch" to collect, and stop collecting, on the run. That's why he's paid the big bucks because it's a precious (paramount) skill knowing when to do it.
Aging is how you further shape that taste profile. Bourbon goes in charred oak barrels (caramels & sugars) and it's time in, and where that barrel is placed, in the warehouse (temperature) determines another part. Scotch uses used barrels (old bourbon, old sherry etc) which adds yet more flavours and their warehouses tend to be cooler (next to the sea) and thus mature more slowly and smoothly. Scotches can have some very complex flavour profiles. Taste is a multi-sensory experience!
Lets not forget that what is being fermented also determines the flavour profile. Whisky is made from fermented beer but there are many ways to make "beer". Part of that is the malting process. Even the smell/taste of peat sometimes used to dry the malts in scotches can come through powerfully.
To me good whisky is not so much for "drinking" but sipping/smelling. It's an acquired taste that comes from knowing and appreciating what's gone into making a good one. One of my favourite single malts I'd never pour more than an ounce into a "Glencairn" style whisky glass (great for smelling the whiskey) for the evening. It's very "peaty" which is why I love it but it's not for everyone. It's flavour & smell is
very complex as you can see from its tasting below - note the nose & palate ;-).
Ardbeg
Uigeadail
“A marriage of younger whiskies aged in ex-bourbon casks with older ex-sherry casks, Uigeadail is considered the favorite among the distillery’s most ardent fans. Pronounced OOGEH-dull.
PRICE $$ · RATING
AGE No age statement
ALC/VOL 54.2%
NOSE Wet stone, antique leather, iodine, smoked meat, and the mustiness of an Army/Navy surplus store; water brings out rubber balloons, caramel chews, and cinnamon. There’s a vague herbaceous quality as well, like fresh-cut mint.
PALATE Full-bodied and sweet up front, then turns toward rubber and charred meat; water dampens the sweetness but brings out dark chocolate and cinnamon notes. The cinnamon continues through the lingering finish.
GENERAL Satisfying, full, and delicious—but only if you’re a serious peat head.”
Excerpt From: Clay Risen. “Single Malt Whisky.”
If I was to go "drinking" for the evening on the other hand I'd reach for the clear vodka for mixing. I'm just too old and crotchety for hang-overs. ;-D