Apple Support:

Using a 70 percent isopropyl alcohol wipe or Clorox Disinfecting Wipes, you may gently wipe the hard, nonporous surfaces of your Apple product, such as the display, keyboard, or other exterior surfaces. Don’t use bleach. Avoid getting moisture in any opening, and don’t submerge your Apple product in any cleaning agents. Don’t use on fabric or leather surfaces.

This is an updated support article from Apple but I’ve always used Clorox Wipes on my water-resistant iPhones.