Diabetes mellitus and/or hyperglycemia are highly prevalent medical conditions in patients hospitalized for coronavirus disease 2019 (COVID-19) and are associated with adverse outcomes. In addition, COVID-19 itself can provoke fluctuating and high glucose levels that can be difficult to manage upon hospitalization. Hospitalized patients with COVID-19 are at high risk of malnutrition due to an increase in nutritional requirements and a severe acute inflammatory response. The management of patients with diabetes/hyperglycemia and COVID-19 is challenging and requires a specific nutritional approach, the purpose of which is to fulfill the nutritional requirements while maintaining an optimal glycemic control. In this study, an expert group of nutritional endocrinologists carried out a qualitative literature review and provided recommendations based on evidence and guidelines, when available, or on their own experience. The optimal care based on these recommendations was compared with the routine bedside care as reported by a panel of physicians (mainly, endocrinologists, geriatricians, and internists) treating patients with diabetes/hyperglycemia and COVID-19 in their daily practice. Early screening and diagnosis, a diabetes-specific therapeutic approach, and a close malnutrition monitoring are essential to improve the clinical outcomes of these patients. In conclusion, the proposed recommendations are intended to provide a useful guide on the clinical management of malnutrition in patients with COVID-19 and diabetes/hyperglycemia, in order to improve their outcomes and accelerate their recovery. The comparison of the recommended optimal care with routine clinical practice could aid to identify gaps in knowledge, implementation difficulties, and areas for improvement in the management of malnutrition in this population.