The 30-year-old, who has already enjoyed spells in England with Arsenal and Stoke, has fully recovered from an illness which threatened to end his career.
"It's great to be here and I'm happy to have signed a short-term deal," Svard told the club's official website.
"I've been out for a long time with a virus, but I'm back and healthy. I'm ready to play games, my match fitness is not 100% but that's improving. Training is good and tough and once I get my chance I will be alright.
"I want to get back to the level that I used to be and play as many games as possible. I'm happy that the team are doing well, it will be tough to get in and the boys look sharp at training. Competition is tough and that's what I need."
Svard played European football with Portuguese side Vitoria Guimaraes and moves to Hansa Rostock and Dutch side Roda JC followed prior to contracting the illness.
Since returning to football he has played for Danish side Silkeborg IF and more recently Sweden's Syrianska.
Blues boss Gareth Ainsworth added: "Sebastian's ex-Arsenal and he's played in Europe. He has an absolute wealth of experience and is a real calm-headed, quality footballer. He's everything that you would want in a midfield general."