Hello~First, your friend needs to be examined by the GP, there could be some reasons
for this such as
Diabetes, urinary track issues, infections, or other issues with the kidneys and/or bladder.
There is a drug called Desmopressin (DDAVP) it reduces urine production at night. But drinking too much liquid with the medication can cause problems, and Desmopressin should be avoided if you have symptoms such as a fever, diarrhea or nausea.