Breeze blocks are easy materials with which to build, but unfortunately they're not energy efficient. Filling the voids within the breeze blocks with insulation isn't very practical because most of the heat conduction through a breeze block wall will happen through the cinder itself. Therefore, the best way to insulate breeze block is to glue rigid insulation to the block. You don't need to insulate the exterior side of the cinder blocks--only insulate the side facing the building's interior.
Measure the area of breeze block to be insulated.
Buy the amount of insulation needed. The rigid insulation comes in sheets that are either 4 by 8 feet or 4 by 10 feet, but they can be cut easily. You can find them at your local hardware store. There are a variety of thicknesses and insulative values that will determine the price. There is no "best" answer on what type of insulative value you should buy, because everyone's needs are different. Decide how well-insulated you want it to be.
Measure the height of the surface you're going to insulate. Mark that length on your foam insulation.
Cut the insulation along the marked line with either a hand saw if it's thick, or a utility knife if it's thin enough.
Apply construction adhesive, found at your local hardware store, to the back of the sheet of insulation that you just cut. Ensure that you lay a 1/8-inch bead of adhesive around the entire perimeter, and also zigzag it across the middle.
Press the insulation into place against the breeze blocks with your hands. Gently press around the perimeter and on the surface of the insulation board.
Repeat as many times as necessary until one side of each breeze block is covered with insulation.