Which in excess is worse when trying to lower body fat %, sugar/added sugar or sodium?
Excess sodium is excreted; it’s not a problem. It can deplete potassium over time, and cause your blood pressure to read a few points higher, but I still supplement sodium at certain times, such as during fasting.
As a rule of thumb, avoiding sodium on labels might improve a poor diet, but it is not a causative factor.
Sugar. That’s because sodium is zero-calorie. It’s not great to consume excessive amounts, but salt alone won’t increase body fat (although the foods salt is added to can). Excess sodium can, however, make you temporarily weigh more, because it causes your body to retain more water. It will also give you a puffier appearance.
On the other hand, sugar is stored as fat if its calories aren’t used right away. Refined carbs are also quickly converted to sugar, so you likely want to reduce those, too.