In fighting sports, a tomato can is a fighter with low skills who is brought in to pad the record of more promising fighters and give them more ring experience. They are expected to lose. Most professional boxers of any note have dozens of wins in their early careers over tomato cans. The name is believed to come from the fact that tomato cans "leak" red fluid (blood) like a can of tomato sauce.

the thing that you don’t have when you’re phones percentage is over 20

N. In a fight, someone who is terribly outmatched by their opponent, and gets beaten quite easily, with no glory going to the victor.

Somebody who is inexperienced at something or is very bad at it. Could also mean a noob