The initiative was designed to highlight the disproportionate level of sexist abuse that female pundits and sporting professionals receive on social media.
The England legends shared their opinions across a range of football matters - but X users had no idea the two were actually using each other's accounts.
Heineken released a video where the pair revealed some of the comments made during the experiment.
Comments left on Scott's account while it was being operated by Neville included users telling her to 'get back in the kitchen', 'concentrate on the girls' league' and 'leave the football to the boys'.
Meanwhile, Scott revealed one user thought one of the comments she made on Neville's account was 'the most objective opinion' he had ever made.
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In response, Neville told Scott: "You make a better Gary Neville than I do."
The results have shown that Scott's account received five times more sexist comments than Neville's, even though they were sharing similar opinions.
European Championship winner Scott - who is also the second most capped Lioness of all time - told X users the experiment had been 'fun' for her 'but less so for Gary'.
She told Associated Press how a number of Lionesses have had to take breaks from social media before major tournaments due to online trolling.
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"It's just sad that you have to remove yourself from a platform just because of keyboard warriors trying to put you down," she said.
In July, the organisation Women in Football carried out a survey which found that 82 per cent of women working in football have experienced discrimination at work.
Neville was shocked by the clear gender bias, but also revealed that his own mother had been banned from playing football with a boys' team in the 1970s.
He told The Guardian: "The idea (women) can't have an opinion on football without having their gender referred to is ridiculous."
At the end of the video, Heineken encouraged fans: "This season, let's keep football opinions about football."
Heineken have also teamed up with an AI tool called Arwen which removes abusive or negative comments from social media accounts as they aim to make the football community a more inclusive space.