Answers

I don't recall where I saw it, but there is a product (similar to door & window flash, but wider) that goes on the plywood, along with a primer. You would need to start the application down at the footing and overlap it to just above grade.

Here is a product that is safe and non-toxic for waterproofing walls and even floors. They have various products for different needs. Hope this is helpful, good luck! 

Product Details

The basement is leaking through the foundation or block wall?  If so, there is nothing you can put on it that will keep the water back if there is enough of it outside the wall.

You need to fix the water issue on the exterior or allow for drainage to the interior in a controlled method. 

You said your basement is made of treated wood? As in there is no concrete or masonry walls below grade?

If that is the case, my first suggestion to you would be to hire a contractor to excavate around your house, demo the basement walls, and replace them with concrete or masonry, followed by correctly installed waterproofing and draining backfill. This will not be an easy or cheap fix. Your insurance may help cover the cost of this repair.

I have never seen a below grade basement built with wood. That just doesn't make sense.

If you do have masonry or concrete walls, and they are leaking, especially through treated plywood that is attached to them, this is an indicator of a more serious problem outside. You may need to excavate around the house and replace the soil with a different type that allows for rapid drainage and prevents any sort of hydraulic pressure from building against your walls. Soil such as sand or gravel, or a mix of the two is ideal for this purpose. Also you should install proper waterproofing against the exterior walls to prevent water from contacting the wall at all.

Hydraulic pressure is incredibly powerful, and if you are experiencing water accumulation and build up sub grade against your house, and it is pushing through the wall, then no product you apply to the wall will stop it or be effective. You have to resolve the cause of the problem first.

Hope this helps.