Balanitis: Given the patient's history of diabetes and the presence of cracks and tenderness on the tip of the penis, balanitis is a strong consideration. It is an inflammation of the glans penis and is more common in diabetic patients due to their increased susceptibility to infections, particularly fungal infections. The fact that the patient has only tried topical antifungal treatment and still experiences symptoms suggests that the condition may not be fully addressed or could be a more complex case.

Fungal Infection (e.g., Candidiasis): Although the patient has tried topical antifungal treatment, the persistence of symptoms could indicate a more severe infection or one that is not fully responsive to the current treatment. Diabetic patients are prone to fungal infections due to their altered glucose metabolism.
Bacterial Infection (e.g., Staphylococcal or Streptococcal): Despite completing courses of cephalexin and doxycycline, the patient still experiences symptoms. This could suggest a resistant bacterial strain or an incomplete treatment course. Bacterial infections can cause significant morbidity in diabetic patients due to their compromised immune status.
Eczema/Dermatitis: This could be a consideration, especially if the patient has a history of atopic diseases. The presence of cracks and tenderness could be indicative of an eczematous process, potentially exacerbated by the diabetic state or previous treatments.

Necrotizing Fasciitis: Although rare, this is a life-threatening condition that requires immediate attention. The patient's diabetic status and the presence of severe pain, especially if it is out of proportion to the physical findings, should raise suspicion for necrotizing fasciitis.
Fournier's Gangrene: This is another severe and potentially life-threatening condition characterized by necrotizing fasciitis of the genitalia. It is more common in diabetic patients and those with compromised immune systems. The patient's symptoms of pain and swelling, particularly if rapidly progressing, should prompt consideration of this diagnosis.

Squamous Cell Carcinoma: Although rare, any persistent lesion or area of concern in the genital area should be evaluated for the possibility of malignancy, especially in immunocompromised patients.
Fixed Drug Eruption: Given the patient's recent medication changes, including the discontinuation of Jardiance, a fixed drug eruption could be considered, especially if the lesions are localized and correspond to areas of medication application or systemic drug reactions.