Only you know your sweet spot for sweet and sour- like this sweet Asian stir-fry
Here's the truth about sweet-and-sour dishes: One cook's sweet is another cook's sour. That is, the balance between the two is highly subjective. 

Take lemonade, the most beloved sweet-and-sour beverage that comes to mind. I prefer it on the tart side, with barely enough sugar to take the edge off. 
My fiance, on the other hand, once said to me, "Who thinks that lemonade should taste like lemon?"

So I suppose I shouldn't have been surprised when I made a recipe for sweet-and-sour cauliflower that called for a half-cup of sugar in the sauce - for a mere four-person serving. I went ahead with it, despite my skepticism, because there was an equal amount of apple-cider vinegar (along with a few other ingredients). 

Sure enough, when the recipe was finished - it's a fairly simple one involving roasting cauliflower, adding chickpeas and coating in the sauce - I found it tilted far too much toward the sweet. I doused it with extra vinegar to compensate.

It's an easy fix, really: I cut the sugar in half. But even more importantly, I added a step: After you whisk together that sauce, please taste. 

Decide where you are on the sweet-and-sour seesaw and add more sugar or more vinegar (or both) until it's right on the money - for you, that is.

The Washington Post