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

Question

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?

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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.

Answer 1

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.

Answer 2

Unfortunately, 〜飲み得ない might be better used in poetry rather than everyday conversation.

And 〜飲むわけにはいかない or 〜飲むわけにはいけない might rather be used more for when something is just "undrinkable" (perhaps something not potable) instead of something you personally cannot (or possibly don't like to) drink.

At any rate, along with @Chocolate's point about「〜飲めないんです。」 another possible option (depending on your audience) could be something simple like: 「私はコーヒーがだめです。」 (And some of those particles can even be dropped...)

Sometimes simplicity is better, in Japanese.

Answer 3

In this particular context, you could just say 「コーヒーは…」 with a troubled voice. Everything else is implied, and your co-worker would probably offer you something else instead.

Answer 4

I would say,"コーヒーは飲めないんです”　I think only this sentence works. It's like "お酒はのめないんです。”This sentence implies that you cannot drink it because it affects your stomach or maybe you're allergic to that. But if that person asks why, I would say,"お腹が痛くなります".or ”気持ちが悪くなります。” If it seriously affects your stomach, I would say, ”体が受け付けません”　It means that my body doesn't accept it.