Flossing on a daily basis removes excess food and plaque that your toothbrush misses. This can help reduce bad breath. If you are still experiencing bad breath, a number of dental issues could be going on like a decayed tooth or periodontal disease. Ask your hygienist if you continue to struggle with bad breath.
Sources: http://www.oralb.com/topics/flossing-bad-breath-killer.aspx
http://www.ada.org/sections/scienceAndResearch/pdfs/forthedentalpatient_sept2012.pdf