They raised eyebrows among traditionalists when they took selfies in the Commons chamber. They broke with convention when they applauded during a parliamentary debate. And now it seems the SNP’s 56 MPs are changing the culture in Westminster in more subtle ways.

New figures show that Irn-Bru sales in parliament have soared since the election of the Scottish National party’s “class of 2015”, the 56 representatives who swept to power in last year’s general election.

Sales of Irn-Bru, which markets itself as “Scotland’s other national drink”, increased by 60% in the year after the party became the third biggest group in parliament – jumping from just six MPs before the election.

The SNP leader, Nicola Sturgeon, with the party’s MPs in Westminster. Photograph: Ben Stansall/AFP/Getty Images

Data released under the Freedom of Information Act shows that bars, cafes and vending machines across the parliamentary estate sold 8,708 cans or bottles in the financial year 2015-16, up from 5,452 the year before.

The figure is more than double the 4,285 bottles and cans of Irn-Bru bought in 2012-13, and MPs, their aides and other parliamentary staff are on course to drink another 8,493 cans or bottles by the end of the financial year next April.

Patrick Grady, the SNP MP for Glasgow North, said the carbonated drink gave politicians “sustenance” through the long days in the Commons. “Barr’s, which produces Irn-Bru, is an independently owned company which plays an important role in the economy of central Scotland and the country as a whole,” he said.

“Famously Scotland is the only country where Coca-Cola is not the biggest selling soft drink. But it looks like we’re making progress in the House of Commons and perhaps the taste will catch on among MPs and staff from south of the border.”

Irn-Bru, which was first produced in Falkirk in 1901, is the third best selling soft drink in the UK, after Coca-Cola and Pepsi. It contains 10.3g of sugar per 100ml, compared to Coca-Cola’s 10.6g and the 11g in Pepsi and 7Up.

An increased demand for the garish orange drink is not the only way the MPs have shaken things up in parliament. Upon arriving in Westminster they were given a corridor of offices previously used by the Liberal Democrats – who saw their number of seats fall by 49 to eight in May 2015 – and began calling it “Freedom Alley”.

In May 2015, the new MPs broke a strict no-photography rule in the Commons chamber by posing for selfies and having pictures taken standing behind the prime minister’s dispatch box. The group was also told by the Commons Speaker, John Bercow, to “show some respect” for parliament’s traditions when they broke with convention and clapped during a parliamentary debate.

In July last year, the Conservative MP for Kettering, Philip Hollobone, complained about the delays in the voting lobbies caused by the arrival of 25 MPs with surnames beginning with Mc, many of whom were Scottish National party MPs.

MPs vote by passing into either the aye or no lobby in the House of Commons and have their names recorded by clerks on alphabetical lists. “A quick analysis shows there are 199 members in the N-Z queue and 236 in the G-M queue. Given you are a G and the chief whip [Mark Harper] is an H, will you ensure that by the time we come back in September [after the summer break], these queue lengths have been equalised?” he said to the then leader of the House of Commons, Chris Grayling.

“The quickest and easiest way to do this would be to consign the 25 members of this house whose surname begins with Mc to the outer darkness of the N-Z queue.”