Paul,
My instructions, which work well for me, are to limit fluids for 8-12 hours before and no fluid intake for 4 hours prior. I last eat at 8 hours ahead, avoiding liquids. The idea is to present with an empty bladder.
Once the 2 hour holding is over and the BCG is voided, I add LOTS of liquids to flush the bladder; it is also time to eat. After an additional 60 to 90 minutes, the BCG really hits me, and urinary symptoms start, indicating the BCG is doing its job.
You may have been told that symptoms MAY increase with additional BCG treatments. For me the increase came at treatment #3 and has continued; some lucky people don't have any urinary symptoms.
Hope this helps,
Best
Jack