I mentioned in my earlier post that caffeine is a cholinesterase inhibitor just like Mestinon is. I thought I better add a caution about that.
Mestinon inhibits acetylcholinesterase, an enzyme whose job it is to "mop up" acetylcholine. So what Mestinon does is give us more acetylcholine for a longer period of time. Caffeine does the same thing, as do the nightshades (potato, tomato, peppers, eggplant).
The problem is that if you drink beverages that have caffeine, or eat chocolate, you don't really know how that will affect you! It's not "regulated" like Mestinon. And there's no way to know what eating a potato will do. It's not like anyone can say that a soda has a 30 mg. equivalent of Mestinon or that a potato has a 60 mg. equivalent of Mestinon!

That's why the nightshades are relatively contraindicated in MG. I've never read about caffeine in relation to MG in any MG website though, unfortunately.
So be careful when you have caffeine or nightshades. Too much acetylcholine isn't good either. You don't want to have a cholinergic crisis. There's no way to know what affect those foods will have on your MG!
When in doubt, talk to your neurologist. Hopefully, they will know about all this.
Annie
I thought I should add that caffeine also increases dopamine, which is why it makes you more mentally alert and "feel good."