McDonald's "large" soft drinks contain 651ml and the biggest offering at Wendy's is around 1200ml, although Wendy's says it doesn't sell many of these mega-drinks.
Fight the Obesity Epidemic spokeswoman Dr Robyn Toomath said it was a great shame the mayor's bid to help halt the growth of New Yorkers' waistlines had been thwarted.
"Nobody believed by itself this would make a significant difference, but it was getting things under way ... It set the direction that there are opportunities for regulation that will make a difference. I hope he fights back."
Mr Bloomberg has vowed to appeal against the New York State Supreme Court ruling, telling reporters Justice Milton Tingling had misinterpreted the new law.
The judge halted the big-drinks ban - on the application of a coalition of unions and industry associations, one of which represents Coca-Cola and another McDonald's - a day before it was to come into effect.
The New York Times said the soft-drink industry had viewed the fate of the new law as a global bellwether on government regulation of sugary drinks.
Boyd Swinburn, the University of Auckland's professor of population nutrition and global health, said the court battle's significance was in the power play it represented between government and industry, "the power politics between public health versus private profit".
"It does show the enormous power of the food industry. It seems to be marching from victory to victory around the world, including New Zealand."
The judge acknowledged the impact of obesity, but agreed with the critics of the unevenness of the new law, which would not apply to convenience stores, allowing them to sell 2-litre bottles of sugary soft drink.
The American Beverage Association said the verdict provided a "sigh of relief" to the people and small businesses that the "arbitrary and unpopular ban" would have harmed.
McDonald's said public health issues required a more collaborative and comprehensive approach than would have been achieved by the new law.
