These are solid, compressed cubes of instant coffee (often pre-sweetened) that you drop into hot water, similar to a bouillon cube.
: Organic Colombian coffee cubes made with panela (unrefined cane sugar), found on Amazon. where to buy coffee blocks
In the coffee industry, a "brick" or "block" typically refers to finely ground espresso-style coffee that has been vacuum-sealed into a hard, solid rectangular shape. These are solid, compressed cubes of instant coffee