Small intestinal bacterial overgrowth (SIBO) is a heterogeneous disorder in which excessive or altered microbial populations in the small intestine coexist with disturbances in motility, anatomy, host defenses, and luminal ecology. Although antibiotics remain the best-studied pharmacological treatment, incomplete response, recurrence, adverse effects, and repeated antimicrobial exposure have stimulated interest in non-antibiotic strategies. This narrative review evaluates clinical evidence for probiotics, Saccharomyces boulardii, berberine, herbal therapies, elemental and conventional dietary interventions, prebiotics/synbiotics, and fermented foods. Evidence syntheses and clinically informative trials were prioritized, with objective breath-test resolution considered separately from symptom improvement. Probiotics have the largest body of direct non-antibiotic clinical evidence, although results are heterogeneous and formulation-specific. Saccharomyces boulardii has shown promising results as monotherapy and as an adjunct to metronidazole in systemic sclerosis-associated SIBO. Berberine has emerged prominently in recent network-level comparisons, while standardized herbal combinations and elemental diets have produced clinically relevant signals but are supported by less robust direct evidence. Low-FODMAP and other dietary strategies may reduce fermentation-related symptoms, but evidence for SIBO eradication is limited. Kefir and kombucha are biologically plausible microbiome-modulating foods, yet SIBO-specific controlled therapeutic trials remain lacking. Overall, non-antibiotic management should be interpreted within a broader pathophysiological framework targeting microbial burden, substrate availability, intestinal motility, mucosal integrity, and underlying predisposing conditions. Symptom improvement, microbiome modification, and objective SIBO eradication should be regarded as related but non-equivalent outcomes.