Yunhee Kim

Arm & Hammer Advance White Toothpaste
With peroxide to whiten and baking soda to clean, this paste releases penetrating bubbles and leaves a minty taste that lasts after you brush. “It brightened my coffee-stained teeth and didn’t make them sensitive,” said one tester.

Time commitment:
The two minutes it takes to brush.

To buy:
$4 for 4.3 ounces, at drugstores.