What could cause my urine to have a fruity, sweet smell?

Unclear. However, in diabetes with poor control a substance called ketones causes some smell like that. Without diabetes, different foods could cause changes in urine characteristics.
Many causes. Diabetes with very high blood sugar

Diabetic keto acidosis- high blood sugar

Maple syrup urine disease- Genetic

Medications & supplements- Vitamin B6 can give fruity smell.

See any of these causes fit in or write again with more details.