from your question I would like to clarify two issues
first .. mouth wash need not be the solution for food settling between teeth.. decay may also be the reason for this.. if so visit your dentist. if not decay it may be due to bone loss (reduced height of bone between two teeth)... in that case mouth wash is not the solution . you can use interproximal floss or brush. depends on extent of bone loss. so for accurate diagnosis you should visit your dentist
second.. mouth was can cause cancer? yes it may cause. don't use alcoholic mouth wash. use non alcoholic one.. also mouth wash should be diluted with water before using..