I had a blender bottle that i haven't cleaned in over 3 months, still had protein in it from the last shake. I opened it up and almost puked, smelled my place up for hours. Scrubbed it out with soap and steaming hot water and it smelt a lot better. Made a shake after my workout and chugged it. When when I finished chugging and started smelling, the awful smell was still there, hit me and I threw up.