A breaker bar is a tool that is used to break loose nuts and bolts that are tightened down too much. If you don't have a breaker bar, there are a few other tools that you can use to get the same result.
One tool that you can use in place of a breaker bar is an impact wrench. Impact wrenches work by using compressed air to drive a hammer inside the housing of the wrench. This hammer then strikes an anvil, which creates a force that is transferred to the socket. This force is what breaks loose the nut or bolt. Impact wrenches are very powerful and can be used on even the most stubborn nuts and bolts.
Another tool that can be used in place of a breaker bar is a ratchet wrench. Ratchet wrenches work by using a gear system to transfer force from the handle to the head of the wrench. This head then turns the socket, which breaks loose the nut or bolt. Ratcheting wrenches are not as powerful as impact wrenches, but they can still be very effective at breaking loose nuts and bolts.
If you don't have either an impact wrench or a ratchet wrench, you can also use a regular wrench in conjunction with some sort of leverage device. A leverage device could be something like a piece of pipe or another length of metal. You would put this device between the handle of the wrench and the head, which would give you more leverage when trying to break loose the nut or bolt. However, this method will require more effort than using an impact wrench or ratchet wrench and is not recommended if you have either of those two tools available