Substrate integrated waveguide (SIW) technology enables the fabrication of millimeter and microwave components and subsystems with the advantages of conventional metal waveguides, but being lighter and easier to integrate along with planar components and circuits. Some attempts have been made to integrate the SIW technology in flexible materials, allowing further integration of the SIW components into garments. There, the metallized cavities have been made with rigid brass eyelets. This reports on the implementation of SIW in flexible substrates by means of conductive yarns, fabrics and knitted strings. Manual manufacturing techniques are applied to produce SIW that fully preserve the flexibility of the substrate. The developed prototypes, being transmission lines and antennas, were validated by S11 and S21 measurements. The obtained results prove that the use of conductive threads through embroidering enables the implementation of more flexible SIW components with efficiencies equal to those fabricated with rigid eyelets. Embroidering is thus a promising technique for manufacturing wearable SIW components.