Final quarter sales at soft drinks group AG Barr, best known for its Irn Bru and Tizer brands, is expected to be around 5% ahead of the previous year after a strong performance from its core brands.Full year like for like growth is expected to be around 10%, the group said in Wednesday's trading update. "The performance in the final quarter is especially pleasing given the strong comparative period in the prior year, the significant operational challenges posed by weather in late November/December and the greater promotional intensity experienced in the market," said the Scottish drinks maker.Rubicon saw revenue grow by over 30% during the year and is now a brand with sales of approximately £50m, double the sales at the time of its acquisition.However AG Barr also issued a cautionary note about pressures on household spending and rising inflation in the UK over the coming year."Despite this difficult economic environment we anticipate further sales growth opportunities through our core brands. The investments we have made in our asset base to improve efficiency together with tight cost control and price increases will continue to help offset rising commodity costs." Across 2011/12 we expect to maintain our focus on delivering above market sales growth, strong cash generation and a robust margin profile, it added.