Two days ago, my uncle was diagnosed with diabetes. but he has chronic kidney disease. which antidiabetic drug is best for patients with ckd?

Why does he need an antibiotic. All meds taken by him should be supervised his doctor.

There are a variety of anti diabetics, old and new that can be used in renal insufficiency, some may have to have doses adjusted, his doctor would be best to pick based on actual numbers at least blood glucose, hemoglobin A1c and estimated filtration rate for his kidneys.