This paper introduces a novel design for suspended anti-resonant acoustic waveguides (SARAWs) that enable controllable Brillouin scattering on-chip. Inspired by optical anti-resonance in hollow-core fibers and acoustic anti-resonance in cylindrical waveguides, SARAWs provide superior acoustic mode confinement and high selectivity, supporting both forward and backward stimulated Brillouin scattering (SBS). The design streamlines fabrication processes and enhances the photon-phonon interaction, leading to significant advancements in integrated photonics. Key achievements include: - **Forward SBS**: A centimeter-scale SARAW supports a large net gain of 6.4 dB with a Brillouin gain coefficient (GB) of 3530 W^-1m^-1, over 2000 times larger than standard single-mode fibers. - **Backward SBS**: Observations of an unprecedented Brillouin frequency shift of 27.6 GHz and a mechanical quality factor (Qm) of up to 1960 in silicon waveguides. The SARAWs are fabricated on a silicon-on-insulator (SOI) platform using a loading-effect etching technique, which simplifies the fabrication process and reduces inhomogeneous broadening of Brillouin resonance. The design and fabrication methods, along with experimental results, demonstrate the effectiveness and flexibility of SARAWs in achieving high-quality acoustic mode confinement and manipulation, opening new avenues for optomechanics, phononic circuits, and hybrid quantum systems.This paper introduces a novel design for suspended anti-resonant acoustic waveguides (SARAWs) that enable controllable Brillouin scattering on-chip. Inspired by optical anti-resonance in hollow-core fibers and acoustic anti-resonance in cylindrical waveguides, SARAWs provide superior acoustic mode confinement and high selectivity, supporting both forward and backward stimulated Brillouin scattering (SBS). The design streamlines fabrication processes and enhances the photon-phonon interaction, leading to significant advancements in integrated photonics. Key achievements include: - **Forward SBS**: A centimeter-scale SARAW supports a large net gain of 6.4 dB with a Brillouin gain coefficient (GB) of 3530 W^-1m^-1, over 2000 times larger than standard single-mode fibers. - **Backward SBS**: Observations of an unprecedented Brillouin frequency shift of 27.6 GHz and a mechanical quality factor (Qm) of up to 1960 in silicon waveguides. The SARAWs are fabricated on a silicon-on-insulator (SOI) platform using a loading-effect etching technique, which simplifies the fabrication process and reduces inhomogeneous broadening of Brillouin resonance. The design and fabrication methods, along with experimental results, demonstrate the effectiveness and flexibility of SARAWs in achieving high-quality acoustic mode confinement and manipulation, opening new avenues for optomechanics, phononic circuits, and hybrid quantum systems.