A standard sandwich tainted with human urine. Commonly used on white bread, its common tell signs are a yellow stain that is concentrated in one area. Unfortunately, there is no way to 100% tell if it is a standard sandwich, or a Pisswich.
The reason is, melted butter or margarine, has the same affects (on white bread). The only surefire way to insure that your sandwich is not a Pisswich, is to eat it, or use a DNA test on all the ingredients in said sandwich/Pisswich.
Common scenarios when one may find a Pisswich, is during sleep overs with friends, parties, weddings, cooking classes, trash cans, and funerals.
Scientist 1: Hey Gary, i think i have found a way to decipher the difference between a Pisswich, and a Sandwich!
Scientist 2: Really?! We must tell the world!
Scientist 1: Right after i eat my turkey-Club Sub. with butter.
Scientist 2: Wait... Butter.... Professor! No!
Scientist 1: Wait... is it... No... i cant tell. I CANT TELL!
Scientist 2: Use the method!
Scientist 1: ... it wont work....!
- THERE IS NO WAY TO TELL -
-SAVE YOURSELF, SAVE YOUR SANDWICHES -