Vinegar is aceti acid diluted in water.
The reaction of vinegar with sodium hydroxide is:
CH3COOH + NaOH ---> CH3COONa + H2O
That is an acid-base reaction.
The speed of reaction is proportional to the concentrations of the reactants.
Then, given thatn when you dilute the vinegar you decrease the concentration of CH3COOH, the rate of reaction will decrease.
Answer: decrease the rate of reaction.