Consumer goods PET (polyethylene terephthalate) bottles are usually thrown away after consumption. A huge number of them ends up somewhere in the environment. In many developing countries PET bottles are used in construction, mainly as fill-in material in concrete or adobe walls. Special purpose PET bottles have been designed and produced earlier that can be stacked in wall systems. In our research we produced a special PET bottle that fulfils the following conditions: (a) produced with blow-moulding technology; (b) good stacking features to eliminate or minimize binding medium between PET bottles; and (c) produced out of recycled PET. This special PET bottle resulted in a series produced and patented brick called PET(b)rick 1.0. We subjected the PET(b)ricks to various tests as done on regular building bricks: stress, pressure, and heat-freeze. PET(b)rick has reasonable resistance to stress greatly dependent on the filling medium, low resistance to pressure, and a small bandwidth of performance in heat-freeze. We have demonstrated stable and safe application of PET(b)ricks in small seating objects. PET(b)rick does not seem suitable as a self-standing wall, but can function as easily stackable fill-in material within a load-bearing structure.