This term derives from the popular annual video game series 'Fifa'. It is used as a dig to describe a video gamer who ONLY scores sweaty(cheap) goals which normally consist of cut backs, double cut backs, lobbed though balls and one-two's...
A sweaty bastard loves footballers with preferably 90+ sprint speed and a formation with 5 at the back.
"You sweaty bastard, 'Insert Insult' " *Rage Quit*
A couple of youtube examples: