What's the most appropriate negative potential form for this situation?


This morning my co-worker asked me if I wanted some coffee. I said, "No
thanks, I can't drink coffee because it upsets my stomach." I was thinking of
how I'd say this in Japanese, but I'm not sure which is the most appropriate
way to say "can't" in this situation.

It seems like saying `飲めない` or `飲むことができない` would only be correct if I
physically couldn't get the coffee down my throat. Since that's not the case
and I'm using "can't" to really mean "I won't because of the undesirable after
effects", those two seem wrong.

Is either of `コーヒーを・は飲み得ない`, `飲むわけにはいかない` more correct and/or preferrable? Or
would something without potential, like `飲みにくい・づらい・がたい` work better?

* * *

**Update** : I knew I was forgetting an option when I wrote this topic. I left
out the possibility of `飲みかねる`, but that sounds _really_ wrong to me.




> Is either of コーヒーを・は飲み得ない, 飲むわけにはいかない more correct and/or preferable?

No.

> Or would something without potential, like 飲みにくい・づらい・がたい work better?

Hmm... no. 飲みにくい/飲みづらい might sound like you're having difficulty
swallowing/drinking because you have some problem in your throat... or maybe
you really hate the smell of coffee...

> Since that's not the case and I'm using "can't" to really mean "I won't
> because of the undesirable after effects", those two seem wrong.

Even so, I think 飲めない would be the best choice.

> "No thanks, I can't drink coffee because it upsets my stomach."

I'd say 「胃が痛くなるから、コーヒーは飲めないんです。」「コーヒー、飲めないんです。おなかの調子が悪くなるんで…」or
maybe「私、コーヒー、おなかに(or胃に)来るからダメなんですよ/無理なんですよ。」etc.




> Is either of コーヒーを・は飲み得ない, 飲むわけにはいかない more correct and/or preferable?

No.

> Or would something without potential, like 飲みにくい・づらい・がたい work better?

Hmm... no. 飲みにくい/飲みづらい might sound like you're having difficulty
swallowing/drinking because you have some problem in your throat... or maybe
you really hate the smell of coffee...

> Since that's not the case and I'm using "can't" to really mean "I won't
> because of the undesirable after effects", those two seem wrong.

Even so, I think 飲めない would be the best choice.

> "No thanks, I can't drink coffee because it upsets my stomach."

I'd say 「胃が痛くなるから、コーヒーは飲めないんです。」「コーヒー、飲めないんです。おなかの調子が悪くなるんで…」or
maybe「私、コーヒー、おなかに(or胃に)来るからダメなんですよ/無理なんですよ。」etc.

