To clean your Nike+ FuelBand SE or first generation FuelBand, use mild soap and water and a soft cloth. Avoid using solvents or detergents.
If the USB connector becomes dirty, use a clean, dry toothbrush to remove surface accumulation. If the toothbrush does not remove the accumulation, use a clean cloth moistened with rubbing alcohol. Wipe dry and allow to air-dry thoroughly.
For especially stubborn accumulation, use a clean cloth moistened with electronics-specific cleaning fluid (available at electronics specialty retailers). Wipe down the USB connectors and allow to air-dry completely.