Type of caulk or filler material to seal gap between block and brick veneer?

[Torn Mind]

Cosmetics don’t matter but there are so many different types of material. Foam, caulk, mortar repair.
It’s the edges of a rectangle under the window. The exposed block will be covered with plywood.

 

[Greenman]

Sounds like a job for polyurethane, but only because it will be protected from the sun. That's strictly a WAG on my part, advice that's worth every cent you paid for it.

I'll check on the contractors forum, several masons there.

 

[jmagg]

Generally, the bottom course should get an aluminum Z flashing starting behind the plywood, then out and over the edge of the brick. The plywood should be brought out to a point where you have enough depth to get backer rod and caulk on all 4 sides where the plywood meets the brick heads.. The depth of the joint should be half the width after the backer rod. Ideally, the siding ( on top of the plywood) should finish up close to the face of the brick. If there is a window on the top side, extra attention on the sill, or even a flashing under the sill may be a good idea. Poly caulk is a good choice.

 

[Torn Mind]

This is what I am going to cover up and the edges still has some good mortar but there are gaps near the top.

 

[13Gigatons]

What's your goal?

To seal it...clean it really well, then use 100% silicone on a entire sheet of 1/4 plywood....then prime and paint the plywood.