/diy/ - Do It Yourself

Friend bought a flipped house. The prev. owner turned this outdoor room into an interior room. Behind these open-faced bricks is a piece of plywood - you can see it if you zoom in. They just screwed it into the bricks, and there's a leak at the bottom right of pic. We fixed leak which was due to pooling water - but this is only a band-aid. This entire wall needs to be properly weather sealed, without removing the bricks. The inside of the wall is very nice so we have to approach it from outside.

TL;DR how would you weather seal this brick facade with a piece of plywood behind it? It doesn't need insulation (Florida) so we can just concrete/rubber spray or anything you think would work well.