Diet soda vs. water: which is better for blood sugar?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion criteria: We will include men, women and non-binary participants with T2D, age 35 years and older, able to provide informed consent, otherwise healthy, who meet the following criteria: * Physician diagnosed type 2 diabetes ≥ 6 months prior to screening * HbA1c 6.5-8.5% at participant screening * Current treatment with lifestyle changes or stable diabetes-related medication levels for the past 3 months * Willingness to provide consent to contact treating physician and physician agreement to refrain from changing diabetes-related medications during the trial (change defined as \> 2 fold change in dose of any 1 hyperglycemic agent or addition or subtraction of an agent) * No physician-directed medication change for 3 months if prescribed medication for lipids or blood pressure * Usual consumers of diet beverages (≥ 3 servings/ week (24 oz.) and the willingness to maintain fidelity of the intervention, and participate in all aspects of the intervention * Not actively looking to make major lifestyle alterations during the study period with stable weight for 2 months (within 3%). Exclusion Criteria: * Type 1 diabetes or suspected type 1 diabetes (lean with polyuria, polydipsia, and weight loss with little response to metformin) * "Secondary" diabetes due to specific causes (e.g. monogenic syndromes, pancreatic surgery, and pancreatitis) * Diabetic Ketoacidosis hospitalization within last 6 months * Severe/major hypoglycemia in the last 3 months-severe/major hypoglycemia is defined as a hypoglycemic event in which patient requires assistance of another person to manage the episode * Glucocorticoid use (prednisone 2.5 mg/d or more or its equivalent) * History of intolerance or allergy to diet beverages or AS or phenylketonuria * Any condition that is known to affect the validity of the glycemic measures (Hba1c) * Major cardiovascular disease event or surgery within past 6 months * Gastrointestinal disease * Renal or liver disease * Current treatment for cancer * Those with major surgery planned or history of bariatric surgery * Antibiotic treatment (\> 6 days) within past 6 months * Currently pregnant (via self-report) or planning to become pregnant during study period; \<1 year postpartum and breast feeding * Current participation in another interventional clinical trial * Previous randomization in this study, * Heavy alcohol consumption (on average \>2 drinks/day for women and \>3 drinks/day for men) * Habitual consumer of SSB ≥ 1 serving / day (8 oz.) * Does not drink diet beverages * BMI \< 20.0 kg/m2