Targeting Pediatric Brain Tumors and Relapsed/Refractory Solid Tumors With Sodium Glucose Cotransporter 2 Inhibitors (SGLT2i)

Inclusion Criteria: * Diagnosis of a recurrent primary brain tumor with no curative therapy available OR diagnosis of relapsed/refractory solid tumor with no curative option and has trialed past a second line of therapy. * Measurable disease per the following: * For patients with brain tumors: measurable disease pediatric Response Assessment in Neuro-Oncology Criteria (RANO) criteria * For patients with solid tumors: measurable disease using response evaluation criteria in solid tumors (RECIST 1.1). Includes patients with diagnoses of relapsed or refractory sarcomas, neuroblastoma, and Wilms tumor. Other rare solid tumors can be discussed with study chair. * Life expectancy \> 12 weeks. * Prior treatment with radiation alone, chemotherapy alone or combined radiation and chemotherapy is allowed. * Patient is between 6 and 21 years old (inclusive) * Patient is capable of swallowing whole pills * Normal bone marrow and organ function as defined below: * Leukocytes ≥ 3,000/mcL * Absolute neutrophil count ≥ 1,500/mcl * Platelets ≥ 100,000/mcl * Total bilirubin ≤ 1.5 x IULN * AST(SGOT)/ALT(SGPT) ≤ 3.0 x IULN * Creatinine ≤ IULN OR creatinine clearance ≥ 60 mL/min/1.73 m\^2 for patients with creatinine levels above institutional normal * Normal room air oxygenation must be documented. If room air oxygen saturation is less than 97%, a diffusion capacity of carbon monoxide (DLCO) of greater than 80%, must be demonstrated. * Karnofsky or Lansky performance score of…