What type of chemical reaction will occur if caustic soda is added to vinegar ?

Caustic soda is the common name of sodium hydroxide (NaOH), which is a strong base.
Vinegar is the dilute solution of acetic acid (CH₃COOH).

Hence, the reaction between caustic soda and vinegar is NEUTRALIZATION.
NaOH + CH₃COOH → CH₃COONa + H₂O

hint: acid + base = salt + water

Neutralisation
Caustic Soda is Sodium Hydroxide (NaOH)
Vinegaar is a solution of Ethanoic (Acetic)Acid (CH3COOH)
Hence the reaction equation is
NaOH + CH3COOH = H2O + CH3COONa

The products are water and sodium ethanoate(acetate)