In the first TV debate between the two men, the pro-UK Better Together leader Alistair Darling was regarded as having secured a narrow victory over Alex Salmond.
But the SNP leader revealed he had a “wee sip” of Lucozade before taking on Mr Darling for the second time on Monday night.
“I haven’t been able to take Lucozade for a year because of my diet so that wee sip before the debate no doubt had an impact,” the First Minister said on Tuesday.
“We got into very substantive subjects we didn’t get the chance three weeks ago – the health service in particular, job creation and the importance of job-creating powers.
“I thought they were substantive subjects.”
Mr Salmond claimed that the No campaign had to “rely on big television things because they’ve got very little on the ground” in the referendum campaign.
He argued that those campaigning for independence “regard these things as an opportunity to shift the focus of the argument on to the things that matter, like the NHS, like jobs for Scotland, because on these things Yes will win”.