Wearable　sweat　sensors　provide　real-time　monitoring　of　biomarkers,　enabling　individuals　to　gain　real-time　insight　into　their　health　status.　Current　sensors　primarily　rely　on　electrochemical　mechanisms,　limiting　their　capacity　for　the　concurrent　detection　of　multiple　analytes.　Surface-enhanced　Raman　scattering　spectroscopy　offers　an　alternative　approach　by　providing　molecular　fingerprint　information　to　facilitate　the　identification　of　intricate　analytes.　In　this　study,　we　combine　a　wearable　Janus　fabric　for　efficient　sweat　collection　and　a　grapefruit　optical　fiber　embedded　with　Ag　nanoparticles　as　a　sensitive　SERS　probe.　The　Janus　fabric　features　a　superhydrophobic　side　in　contact　with　the　skin　and　patterned　superhydrophilic　regions　on　the　opposite　surface,　facilitating　the　unidirectional　flow　of　sweat　toward　these　hydrophilic　zones.　Grapefruit　optical　fibers　feature　sharp　tips　with　the　ability　to　penetrate　transparent　dressings.　Its　microchannels　extract　sweat　through　capillary　force,　and　nanoliter-scale　volumes　of　sweat　are　sufficient　to　completely　fill　them.　The　Raman　signal　of　sweat　components　is　greatly　enhanced　by　the　plasmonic　hot　spots　and　accumulates　along　the　fiber　length.　We　demonstrate　sensitive　detection　of　sodium　lactate　and　urea　in　sweat　with　a　detection　limit　much　lower　than　the　physiological　concentration　levels.　Moreover,　the　platform　shows　its　capability　for　multicomponent　detection　and　extends　to　the　analysis　of　real　human　sweat.