Question

how can we find the hybridisation of Nacl?

Answer 1

By Sp3 hybridisation we find the hybridisation of Nacl.

Answer 2

We cannot find the hybridization of NaCl.

As it is an "ionic compound".  It is composed of two opposite charged ions $Na^+$ and $Cl^-$.

Since, they have "opposite charges" therefore they attract each other and form ionic compound. The concept of hybridization is typically purposed for covalent compounds as it represents the mixing of atomic orbitals to form hybrid orbitals which overlap with each other to form covalent bond by equal "sharing of electrons".