Can sjogren's syndrome cause sores in the back corners if your mouth & a odd taste coming from the back corners?

Possibly: As an autoimmune disease, Sjogrens attacks your mucous producing glands to cause a dry mouth. Since mucous performs an important self cleaning function, it strikes me that food debris or bacteria could establish a long term foothold in the back corners of your mouth. That could certainly cause discomfort and produce odors. Use immaculate oral hygiene and artificial saliva to combat this.