Bruce and Luke, who took over Foxes in 2011, started their coffee roasting business in 2014.
Chloe Chapman, of Botcherby, has been popping in on her way to work at the People First Conference Centre.
She said: "I work at Milbourne Street and so I literally walk past here four days a week. I usually pop into Foxes for my morning coffee.
"We bought a selection of nine doughtnuts on the first day. They went down a treat."
Chloe added: "It is good to see these guys doing it, rather than a big chain."
Colleagues Beth Wilson, Codie Slessor and Amy Rose, from Wragg Mark-Bell Solicitors on Castle Street, made their first visit on Wednesday.
Beth, from Whitehaven, said: "Someone from work mentioned this place had opened so we decided to come and give it a try."
Luke said: "On our opening day, our first customers were two police officers at 5am. We couldn't do them a doughnut because we were just opening up, but they went away with some coffee."