So which ports does Brink uses? I’ve tried playing online few times but it lags like hell. Maybe opening some ports would help.
Oh, btw, does everybody else have crazy ping spikes on server browser menu? I mean one second I get 34 ping, the other 700.
No, opening ports does not help with lag. The only purpose of ports is to allow addressing of specific computers and applications on the network. If something would be wrong here you would not have any connection at all. 
The current ports that brink uses on default is
27015-27016 UDP
8766 UDP
What the post above me said is correct though lag has nothing to do with the ports
but these ports are needed to be opened if you ever plan to host a game to play with a friend