I am wondering since my teeth aren't the best, how could i whiten my teeth naturally overnight?

Use a tray: Tooth whitening is a gradual process and doesn't occur over night. You would need to use custom fitted trays and the whitening gels in the trays to whiten your teeth. Just from a personal observation, i notice that professional swimmers all have nice white teeth from being immersed in the chlorinated pool water. No scientific proof to back this up, but it's my observation.