@northofnorthoftheborder
Hello Canada!😊
I had proton radiation 2 years agon. But now 2 years later all of sudden having some irritation, urgency and frequent urination increase. 
I then read your post and thinking I maybe the culbrit. I drink mor decal coffee that I used to . I did not know acid can cause irritation also, and carbonated beverages (which I have increased also)?
I try to drink no more that 1 bottle of  Cherry Coke Zero (no sugar) but noticed my urination more frequent and urgency leakage since started drinking it. I added the drink to cut down on snacking and enjoy the taste of the cola. 
Will  the caffeine cause the symptoms you mentioned. Seems like I might be the cause of my increase in symptoms of more frequent urnination, urgency, drippling, etc. 
I knew caffience caused a direutic affect on kidneys (from HF doctor) but did not know such a limited amount my contribute to it. I see you say acid in coffee doing it also. I do drink more decaf coffee also.
 Is there any acid in cola? 
I have my 2 year after treatment R/O follow up at UFHPTI on Tuesday. Monday have my PSA lab. Last one was .22 so hoping same or lower but now worried I might have been irriatating that little guy that had gone through so much 2 years ago. 
       
Your experience may be different, but carbonation causes more irritation for me than anything else, so pop might be even worse than coffee/tea. You'll have to experiment a bit.