Originally Posted by After Shock Media

You can and adding sugar is often done by people who want to cut any acidic taste of the tomato. Not sure if it is really needed, specially on jared sauces which often have some sugar anyways.

I would first try just taking some spaghetti sauce from a jar and reduce it first on the stove to thicken it a bit. That will also condense the flavors. *if your starting with jared sauce.

Somehow I know I am misspelling the jar word. Oh well.