1. Something that is or has become hopelessly chaotic, disorganized, complicated, uncontrollable, etc. I feel like the whole tax system is one big soup sandwich. Seriously, how on earth did it ever become this complicated? If the project manager doesn't keep a tight rein from beginning to end, these sprawling projects can quickly turn into soup sandwiches.

2. Someone who is completely unhinged, out of control, or in an incoherent mental state. When I enlisted into the Army, I was nothing but a good-for-nothing soup sandwich. But they taught me to be disciplined, organized, motivated, and resilient in the face of adversity. After seeing how she flipped her lid at her students, everyone is starting to think she's just a soup sandwich.