The company partly owned by News Corporation offered 100-1 and 20-1 odds on major events including the Melbourne Cup, Cox Plate and NRL and AFL markets as part of its launch in October.
The odds were advertised in newspapers, on radio and television, and online.
But that breached strict NSW laws prohibiting the advertisement of any offer of an inducement to participate in a gambling activity.
Liquor and Gaming NSW on Friday said it had issued 14 penalty infringement notices totalling $210,000 - the largest-ever fine of its type for inducements.
Betr has elected to pay the fine.
"This company tried to attract a new customer base and establish a significant market share with promotions that we consider crossed the line, using inducements that had the potential to cause harm to the community," Liquor and Gaming NSW regulatory director Jane Lin said in a statement.
"Wagering operators can legally advertise their products in a variety of ways but they can't advertise or promote inducements such as offers of enhanced odds or bonus bets to entice people to open a betting account."
The regulator said the ads were voluntarily withdrawn after it contacted Betr.
News Corporation's Nationwide News owns 42 per cent of Betr while former Melbourne Storm executive chairman Matthew Tripp and former BetEasy chief executive Andrew Menz hold senior roles.
Betr has been contacted for comment.
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