Can a metallic sphere be charged without rubbing?

 Yes, a metallic sphere can be charged without rubbing by the method of either electrostatici or electrostatic conduction.

Here we discuss electrostatic induction for which given metallic sphere is kept over an insulated stand and a already charged body is brought near to it.
Charges are developed as in figure. Induced free charge are earthed. Now earthing wire is removed and then charged body. As a result bound charges distribute uniformly over the sphere.