The travelling supporters chanted "Oh Brian it's your round" and the Leeds boss responded by going over to them after the full-time whistle and passing a note through the netting.
"Fifty Euros was all I came out with. I'd have given them more if I'd had it. I feel a bit bad actually," the Yorkshire Evening Post quotes McDermott as saying.
Leeds open their campaign with a visit from Brighton & Hove Albion on August 3.