Lettuce, usually shredded, found on hot sandwiches. The lettuce turns into sweattuce when it becomes wilted, wet, or if you will, sweaty. This usually produces disgust in the person who's eating the sandwich.
Sweattuce can also occur if a sandwich has been reheated later on, and the person reheating said sandwich forgot to remove the lettuce before reheating. Microwaved lettuce will always result in sweattuce.
This philly cheese steak would have been delicious
if it weren't for the heaping piles of sweattuce they put on it.
The sweattuce on this sandwich
is extra juicy today.
Oh man, I didn't eat this sandwich
immediately after I ordered it. It's probably gone to sweattuce.