1991 Pontiac Sunbird Brakes not working

If you had no fluid in the master cylinder, then we need to find out why it was empty, but you can rest assure that you have air in the system and it needs to be bled, but im thinking that it may have moisture in there too, witch means you may have to replace the lines, because the moisture will start ruining all of the components and even start, eating the system from the inside out. Lets hope that it hasnt come to that yet. Try bleeding your system thoroughly, look for leaks too because you may have a popped brake line, (the reason the master cylinder was empty)