Fergie maintains those killer abs with tons of stomach crunches – and raw apple cider vinegar. The Grammy nominee tells PEOPLE that twice a day, after lunch and after dinner, she swallows 2 tablespoons of the bitter liquid. "Vinegar appears to slow down the rate of foods emptying from the stomach," Pachella explains, "but it certainly doesn't taste good by itself. Instead, I recommend a salad with olive oil, vinegar, herbs and spices with your meal."