The other magic ingredient is salt. A tiny pinch of salt can balance out sour and bitter flavors in surprising ways, and be otherwise undetectable. I’ve “fixed” a lot of cocktails that way.

This reminds me of when a student pub hosted a wedding party. As we got to the dance floor there were drinks on offer. I grabbed a Cuba Libre and essentially went "oh, that's the roughest on I've had, must be cheap cola on truly awful booze". Kept on sipping. Someone else complained. Then another one. We go back to investigate. Bartender has a taste. Grimacing.

Like bad and maybe salty?

Takes a minute before they track it down. They'd mixed up the salted ice cubes they used to keep champagne cold with the ones they use for drinks.

That one was rough. I had politely worked through my drink before we launched the investigation. Good party though and I did get a new drink which tasted fine.

I'm sure a tiny pinch can do wonders. Salted cubes, not recommended.

A little pinch of salt in the water is recommended for drip coffee as well to add a pop to the flavors and reduce bitterness.

weirdly, a few drops of maraschino liqueur (I go for Lazzaroni) can "stretch" out the flavors of a lot of "brown" liquors. I have no idea why. It kind of adds a strange almond-ish flavor on the finish, though.