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. Be sure to carefully follow instructions for using this drug.
Desmopressin is given orally as a tablet and is only for patients over 5 years old. According to the Food and Drug Administration, nasal spray formulations of Desmopressin (Noctiva, others) are no longer recommended for treatment of bed-wetting due to the risk of serious side effects.
Again, however, I can't stress enough that your friend should be checked by the GP, as an adult , this can signal other issues that need fairly prompt attention.