Vitamin B2 (riboflavin) commonly causes bright or fluorescent yellow urine, especially after a B-complex or multivitamin. It is harmless and reflects excess water-soluble riboflavin being excreted in urine. NIH riboflavin information

Seek medical advice if the color persists without supplements or is accompanied by pain, fever, blood, very dark brown urine, or yellowing of the eyes/skin.