Background: Myofunctional therapy has emerged as a treatment option for obstructive sleep apnea (OSA). The Iowa Oral Performance Instrument (IOPI) enables objective measurement of lingual and orofacial muscle strength, although it was originally designed for evaluating dysphagia. OSA is frequently associated with a hypotonic phenotype characterized by reduced strength in upper airway muscles, but its identification remains unclear. Objective: We evaluated the usefulness of IOPI measurements in identifying hypotonic phenotypes among patients with obstructive sleep apnea (OSA). Methods: We carried out a cross-sectional study analyzing the relationship between IOPI scores, sleep polygraphy metrics—such as the apnea–hypopnea index (AHI)—and findings from physical examination. In addition to the standard IOPI protocol, we introduced novel maneuvers aimed at providing a more comprehensive assessment of oropharyngeal muscle function. Results: Although IOPI conventional maneuvers showed no clear association with AHI or ODI, the inferior tongue maneuver showed higher awake tongue strength, with a statistically significant correlation to both AHI (r = 0.2873; p = 0.008) and ODI (r = 0.2495; p = 0.032). Performing each exercise three times yielded highly consistent results across trials (r > 0.94), but did not significantly alter the overall outcome. Interestingly, lower tongue strength values were observed in patients with a high-arched palate (p < 0.05), whereas no relevant associations were found with the presence of a restricted lingual frenulum or CPAP use. Conclusions: Incorporating specific IOPI maneuvers, especially the inferior tongue exercise, may provide additional insight into muscle function in OSA. Selective repetition is advisable for borderline values.