Heat intolerance is pretty common with folks with MS. It was explained to me this way: Our internal thermostats are "broke" Perspiration -- the body's natural way of cooling -- doesn't happen, or doesn't happen efficiently. Sweat, when it rises to the skin's surface, is evaporated, and that's what provides the cooling, but if we don't sweat, then our body quickly overheats. This is particularly true in hot humid weather, or hot humid conditions (like hot baths, showers, hot tubs, saunas, that sort of thing..)
So many of us avoid all those things, or dramatically limit our exposure to them.
What can happen if you do get overheated (other than sunstroke, a VERY serious condition!) is that whatever symptoms you normally experience with the MS will intensify, until you cool back down.
I always take water with me, and if I know I'll be out in the sun, a cooler with water, ice, wet cloths to put on my head or back of my neck or wrist, until I can get inside again.
As for alcohol: I don't have any serious alcohol intolerance, like you're describing. I can't drink as much as I could as a young person in my 20's...I'm 60, now .. but it hasn't caused any sort of problem. Are you on any meds? Sometimes meds and alcohol don't mix.
...I am not a doctor, nor health professional, and don't pretend to be one, here.....