Hybridization of central atom in CO₂ is same as the hybridization of central atom in

The structure of CO₂ is:

$\mathrm{O}=\mathrm{C}=\mathrm{O}$

Here, hybridization of C is sp. 

Structure of ethyne is:

$\mathrm{HC}\equiv \mathrm{CH}$

Here also, both carbon atoms have sp hybridization.