A long day of running errands left your feet aching and fatigued and the quick remedy is to soak them in warm water with powdered mustard. To do: Pour 2 liters of hot tap water into a basin and stir in 2 tablespoons of powdered mustard. Then soak your tired feet for 5 to 10 minutes. A compound found in mustard seeds, Sinigrin, helps reduce inflammation and stimulates blood flow in the feet to help put the pep back in your step. Plus, mustard's antimicrobial and antifungal properties will keep your feet smelling fresh.