I ordered the U/U from the start because I didn’t want any artificial sweetener in my food and tried it the first time pure. Impossible to drink, took me 4 hours for one shake.
What is working best for me and also what is really the only thing I tested so far which changes the taste noticeable is pure cocoa powder. At first I also added real sugar to it, 1 teaspoon per ~500g, now I switched to coconut blossom sugar but sometimes I also use honey.
So if you are okay with cocoa powder you should give it a shot. You need to add a very generous teaspoon of it though.