This can be set against a rise of 0.3% in retail sales volume generally for September.
Bar sales were down 2.0% in value compared to August.
On an annual basis bar sales volumes were up 5.8% compared to September 2014 while they were up 6% in value.
Final CSO figures for August indicate a 6.0% annual rise in bar volumes accompanied by a 6.4% rise in value.
Bar sales volumes were down 0.5% compared to July while values rose 0.3%.
The three-month period July to September showed a 7.1% rise in bar sales volumes compared to the July-September period in 2014 while bar sales values were up 7.4%.
Compared to the previous April to June period bar sales volumes were up 2.0% while bar sales values were up 2.7%.