A brief rinse with water would be good enough for me. I am pretty sure that a bucket full of yummy rotting kitchen scraps can win out over any trace of health guard this side of nuclear meltdown control of odour causeing bacteria.

My guess is you could leave the bucket half full of kitty litter and just add the bedding and food right on top and get a thriving bin. Kitty litter is probably clay, or newspaper, or wheat hulls (?) with charcoal. There could be some baking soda I will leave for others to comment upon. If baking soda is even in the product.

Of more concern is the smell when opening the sealed bins after storing for a few months. Maybe check out bokashi.