Media tracking company The Global Language Monitor (GLM) said in a "Sochi 2014 Ambush Marketing Outlook" that official sponsors faced considerable pressure from those who contributed nothing to the Olympic movement.
With six months to go before the Games open in Russia's Black Sea resort on February 7, the report found that 10 of the top 15 companies it ranked by brand affiliation with Sochi were non-Olympic partners.
In the same top 20 list, Olympic sponsors filled the bottom five places.
For Rio, the 'ambushers' led Olympic worldwide partners by a margin of approximately 3:1 in August.
"The Olympics have the ability of make, break, energize, or hasten the decline of global brands," said GLM president Paul JJ Payack.
"Successfully affiliating one's brand with the Olympics can result in billions of dollars in revenue differential."
GLM put the cost of being a top Olympic partner at more than $1 billion over the four year period between Summer or Winter Games.
That cost includes rights fees payable to the International Olympic Committee (IOC), the cost of advertising, merchandising and other marketing activities.
Sochi has 10 worldwide Olympic partners - Proctor&Gamble, Samsung, GE, McDonald's, Panasonic, Coca Cola, Visa, Atos, Dow Chemical and Omega.
GLM, which carried out an analysis of how often brand names were linked to the Olympics in global print and electronic media as well as Twitter and the 'blogosphere', said there appeared to be a serious 'value leak' of Olympic brand equity.
However it added that not all of the non-affiliated brands were ambush marketers, those who deliberately attempt to link their names to the Games, but rather benefiting by size and reputation before advertising campaigns by official sponsors kicked in.
Companies like energy drink Red Bull, a rival of Olympic sponsor Coca Cola, are active in several sports including Formula One where they are the reigning world champions.
Sochi has a grand prix scheduled for next year and Red Bull's world champion Sebastian Vettel visited the Olympic Park location in May.
"Companies like that are good at leveraging whatever it is they are connected to other sports," Payack told Reuters from Austin, Texas.
The IOC is fiercely protective of its symbols and mascots, even limiting word pairings and combinations that could be seen as referring to the Games.
Rule 40 of the Olympic charter also forbids athletes from taking part in advertising for anyone except sponsors during a Games.
(Reporting by Alan Baldwin, editing by Ossian Shine)
