Alcohol never helps the situation. But occassionally having a few drinks does not appear to have a significant impact. At least, not from many patient reports over many years.

Interestingly studies show that eating certain foods and COVID shots early into ICI journeys, and adding CBM588 and akkermansia and camu camu (to boost aforementioned) can boost ICI significantly.
https://www.nature.com/articles/s41522-025-00819-2
https://pmc.ncbi.nlm.nih.gov/articles/PMC12325897
https://www.nature.com/articles/s41591-024-03086-4
https://pmc.ncbi.nlm.nih.gov/articles/PMC9133437
https://pmc.ncbi.nlm.nih.gov/articles/PMC10528119
https://ascopubs.org/doi/10.1200/JCO.2024.42.4_suppl.TPS491
https://www.nature.com/articles/s41586-025-09655-y
https://www.sciencedirect.com/science/article/abs/pii/S1040842825002963
A key factor is that chemo before ICI and antibiotics due to chemo induced illness (such as AKIs/sepsis) depletes the gut of beneficial bacteria. CBM588 akkermansia camu camu shocktherapy for me restored this in weeks. I went from terrible painful constipation to regular stool.