As I have mentioned, there is a little joke about Cognac and added sugar (and oak extract). As we know, sugar really does change many person's perception of the quality of the product, since it rounds the corners of the spirit, so to speak, and lessens that "alcohol burn" as well. People perceive the resulting spirit as more "smooth" and "easy to drink".
I was travelling recently, and bought on purpose some "not-so-good" gin and vodka to try and to use as a foundation for some not-so-refined frozen cocktails to be enjoyed on a hot summer's day.
Price v quality - these products are certainly of excellent value. Used on their own for sipping / on the rocks, well...Suffice to say, their lack of refinement shows in the mouthfeel. The vodka is quite harsh, not so "smooth" as more expensive products, and the gin - eh, contains the right spices for a traditional London dry gin, but...again, it tastes rather harsh. What to do? BLINK (idea lamp inside my head lights up)!!!!! Let me "pimp" them!!!!

For the vodka, I used ordinary white sugar, with the objective of taming down the harsh edge from the taste of this, uh, less refined spirit. Side by side, I have a few super-premium and premium vodkas (Finlandia, Absolut, Russki Standard Platinum, Ice Queen). I simply add a bit of sugar, and mix until sugar is dissolved. A slow process, but I have time to kill..
RESULT: By tasting tiny amounts of various products, and adding what I perceived as sufficient amount to take off the edge, I was able to vastly "improve" the product to a level where myself and a few mates could no longer easily at least differentiate the product from the rest. Voila! One cheap vodka brought up a notch in "quality"!! The spirit has no flavour added, since it is a vodka, but the added sweetness really makes it seem smoother and more pleasant to sip on the rocks or cooled as such.
How about the gin then? Well, same same, but I also could not resist infusing a little more spices in the gin, to add flavour. Juniper berries, sitrus peel - in tiny amounts - go in the bottle for a brief period. After a day, I note a subtle difference in the taste, mmm - more spicy! Ahh, thats more like it, but the spirit is still harsh...sugar, my old nemesis, time for you to do your magic!
RESULT: It is not the best gin, but if I poured it to an empty bottle of a "decent" brand and served it, I would wager a fair amount of money that nobody would be able to tell the difference. As is, I made 2 versions of it (with varying degrees of sugar and spices mixtures).
Are these now fine spirits? NO.
Are they more drinkable - because the original "as is" experience was not far from dreadful? YES.
Would I do this to any good "as is" product? NEVER.
Such alchemy is and should be reserved for the little chemists at home, like me - not to large companies trying to get us to pay extra amount of $$$$ for a crappy product that's doctored to be drinkable...