You don't need an antibacterial, you need the right bacteria in there. Aerobic bacteria. Your tank is starved for oxygen and will go anaerobic unless you provide an aerobic nutrient.
Rinse the tank with several cycles of pump out and water to get any existing chemicals out of there. Make sure you tank vent is clear and free-flowing. Find a nitrate-based additive (KO works well) and add that to the tank after each pump out to make sure the good bacteria (aerobic) get what they need to keep the tank aerobic and nitrogen gas blanketed.
No bleach, no antibacterials, no formaldehyde. Clean the bowl when pumped dry. Pump the waste clear of your hoses and into the tank. Most people don't flush with enough water.