What is the difference between these two? No difference at all?
When I just drink a cup of wine, I get drunk.
When I drink just a cup of wine, I get drunk.
Plus if those justs were replaced with 'even', how would the meaning of the sentence change?
Here you want to emphasize on the fact that you get drunk with only a cup of wine, so put "just" before "a cup of wine". I think No. 2 is better.
And if you want to use "even" in your sentence, rewrite it this way:
Even a cup of wine makes me drunk.
or
Even with a cup of wine, I get drunk.
or
I get drunk even with a cup of wine.
So to you these sounds awkward?
When I even drink a cup of wine, I get drunk.
When I drink even a cup of wine, I get drunk.
Not awkward, but prefer to say:
Even when I drink a cup of wine, I get drunk.
or
I get drunk even when I drink a cup of wine