How to offset sweetness in a sauce? I recently tried a recipe for Mongolian BBQ that I found online.  The sauce consists of garlic, ginger, water, soy sauce, cornstarch, and the main ingredient is 2/3 cup of brown sugar.  While it tasted good, I was wondering what I could add to offset the sweetness, perhaps giving it a bit of heat?

The garlic and ginger are first sauteed in vegetable oil before the other ingredients are added.  Would using hot chili oil instead of vegetable oil give it any heat?

What other ideas would you recommend?
American versions of Mongolian BBQ are often pretty sweet (this doesn't sound like an authentic recipe). More soy sauce (or more of everything but the sugar) would cut the sweetness. Chili oil would certainly give it heat, but isn't going to temper the sweetness much. Any of the following would offset the sweetness and be appropriate for this type of dish:


Any tart apple (a common ingredient in the Japanese version of Mongolian BBQ)
Onions (not caramelized)
Rice wine vinegar