Welcome Ness, I understand because I hate raw coffee myself.. there is nothing to like about its taste as its mostly always bitter. What you could do as a start is to decrease the amount of concentration of powder, then add on the sugar cubes.. basically tweak it as much as possible to maintain a sweetness-caffeine balance. More powder just makes it much worse. I've also used a kind of concentrated palm-sugar essence to the coffee which spreads the sweetness evenly across and hence very usable for black coffee.
The trick is also in the temperature, since black coffee is essentially water, boiling hot is certainly not the way to have it.. it should be a bit more than lukewarm at best. Also it'll take a few months for you to get used to the thin consistency compared to milk. Again I say do not use much coffee powder since coffee is acidic and without milk (a neutralizer) it'll unleash all of the acidity in the stomach in the long run. You do have milk substitutes like almond, soy etc but they wont come close in taste, but you can try them all for a week each and see what combination truly appeals to you.
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