What can we use to put out a fire that involves sodium or any alkali metals. I know we can't use water as sodium reacts violently with water, then what else can we use?

I don't think, from the way the problem is worded, that Na metal must be involved. The problem states, "that involves sodium or any alkali metals." I think that means Na2CO3 or NaHCO3 (K2CO3 or KHCO3 or CaCO3) could be used. These, upon heating, will evolve CO2 and that can act to extinguish a fire.