What recipe are you following?
In addition to adding some flavor to the pork belly, sugar can offset the bitterness of the salt carrier of the cure. I would think you could reduce or omit the sugar called for but this might mean a longer soak-out time. You don't want to change the amount of salt or pink salt the recipe requires. You could also add other seasonings, blavk pepper, garlic powder, fenugreek or others.
BTW if your recipe calls for Tenderquick, it has some sugar added. If you use a pink salt cure any sugar is called out as a separate ingredient.
EDIT - Let's say you went with a cure which contained 1% sugar, that would mean that 1 pound of bacon would receive 4.54 grams of sugar. A sugar molecule is too large to actually permeate the meat, only water and salts can do that, so sugar remains near-surface during the cure time and most of that will go away during rinsing and soaking.