You really don't need to do anything. I am so sorry, I know that sounds cold. However, there are consequences to not taking care of yourself, and now he is suffering those consequences. I am so sorry.
I would let him know you feel for him, but that it does not negate what is going on. Easier said than done, I completely get that.
And....they won't give him chemo w/out doing a biopsy first, especially if they suspect it's simply a cyst. And yes, beer is full of carbs that contributes to high blood sugar.
Tight hugs to you my friend.