Devon-based coffee firm Rugga Coffee created the new blend to raise cash for the My Name’5 Doddie Foundation, set up by Weir after he was diagnosed with the incurable disease.
And to help launch it, Barclay, who was capped 76 times for Scotland, served up coffees in Edinburgh.
Meanwhile, Rugga Coffee boss Steve Edwards delivered the new blend to Weir’s former Scotland teammate, Kenny Logan, and his TV presenter wife, Gabby.
Speaking about the venture. Barclay said: “I’d do anything for Doddie, so I was buzzing to get the chance to serve his new coffee, and I was even more buzzing after I tried it.
“It’s great to see how the wider rugby community has rallied behind him and have done whatever they can to help raise funds and awareness.
“When I spoke to people today, it once again reminded me not only how much love people have for coffee, but also how much love they have for Doddie. I think this will prove to be very popular.”
Mr Edwards stated: “I grew up playing rugby in the second row watching Doddie, admiring the way that he played.
“Because of what Doddie’s going through now, and because I lost a close family member to MND, this is a cause very close to my heart.”
A percentage of the profits from sales of the Doddie’5 blend will go to his foundation.