Evidence suggests that COVID-19 infection increases the risk of type 1 (T1D) and type 2 diabetes (T2D). Diabetes, in turn, increases COVID-19 susceptibility and contributes to increased COVID-19 morbidity and mortality. Oxidative stress (OxS) has emerged as a common factor driving the pathogenesis of diabetes and COVID-19 caused by the severe acute respiratory syndrome coronavirus (SARS-CoV-2). The mechanistic links between OxS, T2D, and COVID-19 have primarily been studied in adults and will be summarized in this review. However, we suggest that studying these interconnections in children and young adults is critical since early intervention is optimal for improving outcomes. At the height of the pandemic, COVID-19 was a leading cause of death in children and young people, and people in this age group are as susceptible to COVID-19 as adults and the elderly. Glutathione (GSH) is the primary water-soluble intracellular antioxidant and can be deficient in both diabetes and COVID-19. GSH is a tripeptide containing cysteine (CYS), glutamic acid (GLU), and glycine (GLY). Strategies to increase GSH levels may be beneficial in helping to manage COVID-19-induced diabetes as well as diabetes-induced COVID-19 risk. Dietary supplementation with GlyNAC may be optimal since it contains two metabolic GSH precursors, i.e., n-acetyl-l-cysteine (NAC) and GLY.