The song itself is a classic example of a young man who just wants to play ball. The protagonist in the song (Brian) asks the crowd to pick him, and also fill his cup. This represents his life of rock and roll and the way he portrays it. He asks the listener to mix in the sin and join the crowd. Ethically, peer pressure should not be encouraged, although Brian brings up many good points about party time.
He then wants to play some ball, whilst shooting the wall. Pretty self-explanatory. He then reaches out to Sid, who knows who Sid is? A lost Brother? His Father? An old friend? Maybe you are Sid. This is a question that Brian poses, and only he knows the answer. What we do know, is that Brian is in love with Sid. Taking us back to the romance of the 80's, classic AC/DC.
Brian then goes on to repeat the phrase "Let's play ball". Potentially chronicling the struggles of his life. Maybe it is a plea? He just wants to play ball although no one will let him. Brian, we salute you and your plight play ball.