The Children's Hope Foundation was one of several businesses in the Eagle Workshops in the East End ransacked by burglars, two weeks ahead of its official opening by Kate Adie.
Thousands of pounds-worth of equipment and cash were stolen.
Viv Watts, regional executive of the Children's Hope Foundation, said: "It's just despicable that these people could have stolen money from a charity.
"They went straight for the cash – there were computers and other equipment around but they took away the money that would go directly towards helping people in need.
"But all the money taken from people's donations is gone for good, we can't ever get it back."
Other businesses housed in the Eagle Workshops are considering leaving the city centre after the break-in.
Tony Buckley, managing director of Gibbons butchers, discovered the break-in when he arrived shortly before 7am on Monday.
He said: "The front door was fine but the inside doors to the offices had been smashed in.
"The thieves got away with our petty cash safe which had a few hundred pounds in it but I think others got hit worse."
Gibbons' co-owner Ian Gibbons said it moved to the Eagle Tavern in June.
He said: "Perhaps we will have to rethink about moving out because of all the crime.
"There is a lot of money and development being invested with business and luxury apartments springing up in this area but at the moment the security in place doesn't seem to reflect that."
Ian Wright, co-owner of New World Designs graphic design firm, lost thousands of pounds-worth of equipment.
He said: "We are very seriously considering whether we want to leave the city centre because we are paying a lot of money but the risks might be too high."
Police have launched an investigation.
The Eagle Workshops, on the site of the former Eagle Tavern, dates back to the 1670s.
Part of a £5.6million award-winning restoration, along with the adjoining Exchange Building, the workshops have been home to several businesses since being completed this year.
Sunderland-born Kate Adie OBE is set to formally open the buildings on Thursday, November 18, for owners North East Civic Trust.
The Echo contacted the trust but it was unable to comment.