Baking soda and water makes a great teeth whitening toothpaste that will help get your teeth whiter within one to 2 days depending on how bad your teeth are.
If the teeth aren't really dirty or stained then the baking soda toothpaste should get your teeth noticeably whiter in one day.
But if your teeth are really stained then it might take up to a month of brushing your teeth with the baking soda paste to see the results and get your teeth whiter again.
Another way is to go to the dentist and pay for a professional teeth cleaning which will have your teeth cleaned in one day but it's costly for a dentist to clean your teeth.