A quarter of community sporting clubs examined in a Hunter-based study had sponsorship deals with fast food or sweet drink companies.
The research has heightened concerns about unhealthy food being marketed to children.
The study examined community sporting clubs with senior and junior teams in the codes of soccer, AFL, rugby league and rugby union.
Banners were the most common place for advertisements for sweetened drinks.
Participating clubs were observed on a weekend game day when junior sport teams were active.
They recorded any visible advertisement, promotion or sponsorship on sporting club signs, banners, equipment or uniforms.
Fast food sponsorship related to outlets such as McDonald's and KFC.
Sweetened-drink sponsorship referred to soft drinks, sports drinks and cordials.
Associate Professor Luke Wolfenden said any marketing of products high in fat, salt and sugar at sporting clubs was inconsistent with World Health Organisation recommendations.
"This should be avoided to support the development of healthy dietary habits in children," said Associate Professor Wolfenden, a University of Newcastle researcher.
"Any form of promotion of fast food at children's sporting events and venues has the potential to adversely influence child dietary habits."
He believed this issue, like many public health problems, required a "whole of community response".
"Government, industry, sporting clubs, parents and the community all have a role to play," he said.
The research paper was titled, "Exposure to fast-food and sweetened-drink marketing at community sports clubs in Australia".
It was published in the peer-reviewed journal, Public Health Research and Practice.
Associate Professor Wolfenden said it was "important not to over-interpret the study findings".
"This was a small study undertaken in one small region of NSW and the clubs participating may not represent typical clubs in the region," he said.
Of the 39 clubs examined, 10 [26 per cent] were found to have some form of fast-food or sweetened-beverage marketing or sponsorship.
These clubs had one or more recorded advertisement, promotion or sponsorship for fast food and/or sweetened drinks.
Seven had only fast food, two had only sweetened drinks and one had both.
McDonald's was the most common fast-food outlet marketed.
Fast-food marketing was more common in rugby league and rugby union clubs, compared with other clubs in the study.
There were no significant differences between the codes when it came to the prevalence of sweetened-drink marketing.
Junk-food marketing may be more widespread on player awards and club communication on websites, email, social media and newsletters.
The researchers recommended that policymakers and public health practitioners prioritise efforts to replace sponsorship from "companies that promote behaviours that are not in the interests of child health".
They further recommended financial incentives to support clubs to phase out unhealthy food sponsorship.
Asked what else should be done about the matter, Associate Professor Wolfenden cited the Obesity Policy Coalition's work.
The coalition asserts that companies use sponsorship relationships to "project an altruistic image".
Nonetheless, research has shown that corporations do not confuse sponsorship with philanthropy.
They expect product exclusivity and opportunities to boost brand awareness in return for their sponsorship dollars.
"They see sponsorship as a means not only to enhance national image but to project the company as a caring organisation involved with its community," the coalition said.
It said federal and state governments must establish a scheme to provide financial incentives to children's sporting organisations and community clubs to reject unhealthy food sponsorship and transition to other financial partners.
They should also develop healthy sponsor criteria to support clubs.