Wiktionary
n. 1 (context slang boxing derogatory English) An inferior fighter in the sport of boxing; The insinuation is that an up and coming fighter takes on a “tomato can” to burnish his reputation and record. 2 (context slang boxing English) A boxer who “take a dive” or loses a fight on purpose.
Wikipedia
In boxing, kickboxing or mixed martial arts, "tomato can" or simply "tomato" or "can" is an idiom for a fighter with poor or diminished skills (at least when compared with the opponent they are placed against) who may be considered an easy opponent to defeat, or a "guaranteed win." Fights with "tomato cans" can be arranged to inflate the win total of a professional fighter. The phrase originates in the childhood pastime of kicking a can down the street—a boxer is advancing his career with minimal effort by defeating a "tomato can" and notching a win. "Tomato" refers to blood: "knock a tomato can over, and red stuff spills out."
Usage examples of "tomato can".
And believe me, I think this tomato can beat a supplement for taste any day.
Johnny fashioned a makeshift cage out of a tomato can which he punched full of holes, and they proceeded with their cave exploration.
And then we dipped a sickening wing, leaving my stomach back up there at ten o'clock high, stood precariously still on big flaps, then steadied down into the runway lights streaming by bumped and squeaked, brake-blasted, and everybody began smiling at everybody for no special reason, and began gathering gear, as the hope-you-enjoyed-your-flight-aboard-the speech came on, articulated by one of our stewardesses over a PA system which seemed to be constructed of an empty tomato can and a piece of waxed string.
The cabin cruiser was essentially a lightly constructed yacht and offered only slightly more obstruction to a bullet from an army rifle than a tomato can.
Patch gave the red chair seat a final brown swipe and dropped the brush into a tomato can.
Then, standing in the big car, dimly lighted by the butt of a candle set in an old tomato can, they faced the stranger.