Spent coffee grounds (coffee sludge) is the most common recycled material obtained in the production of instant coffee. Thus, about 6 million tons of coffee sludge are generated annually. The purpose of this study was to evaluate the use of coffee sludge as an innovative functional food ingredient in flour confectionery products and to study the effect of coffee sludge and its chemical components on sensory properties, volatile components and rheological properties of the final product. Spent coffee grounds contain significant amounts of insoluble dietary fiber, proteins, lipids, ash and lower glycemic sugars. Mixing wheat flour with coffee sludge did not affect significantly the rheological properties of the dough and overall acceptability of the final product. Thus, the obtained biscuits can be recommended for patients with diseases associated with obesity and diabetes, as well as for people who prefer low-calorie foods.