While neither Kenny or Spenny technically cheated based on their own rules, a case could be made that both cheated by getting caught commiting crimes.
Spenny got caught twice. The first time he was caught stealing some poor woman's dog. The second time he was caught stealing a bonnet. When he was caught stealing the bonnet, he was drunk and started a racist rant about how "they" don't even know when they're being robbed.
Kenny got caught by a police car driving past, when he threw the newspapers in the air, after sticking a Kenny vs Spenny poster on a light pole. He wasn't charged and got away with it.
8th Jan 2008 / Season 4 Episode 10
Kenny performed lots of minor, petty crimes, for example loitering, spitting and driving without a seatbelt. Spenny preferred to stick to more politically correct, "good" crimes, until he became drunk while drinking in public. Although Kenny had a large lead, he received a parking ticket from a police officer, and was disqualified for being "busted". (The rules of the competition stated that if they were caught committing a crime, they would be disqualified).