How do you express "have to" in order to talk about a non-obligatory, but obvious course of action?

Question

In English, "has to" and "have to" serve to express obligations (as in "must", like in the classic example of having to do homework), and also work for when one wants to express something that isn't an obligation - but is otherwise a highly reasonable, obvious, or even inevitable choice of action. Consider the examples:

Before going on a long car ride: "You have to eat something before we head out." (Suggestion as to the only reasonable action)

Upon learning information that's relevant to a friend: "I have to call her to let her know." (Not an obligation, but an action that naturally follows)

Or, for a more casual example, using a sports game:

"You'll have to hide after such an embarrassing defeat."

I hope it's clear, especially with this last example, that I'm basically asking how to express that someone certainly has to do an action, even if the person isn't actually obligated to, but is otherwise understood as having their hand forced by, for instance, personal inclinations.

For example I am not obligated to post here my every doubt, and can still learn Japanese without having an answer to this question - but if I can't clear it up by myself, it's my best option to consult others ("I'll have to ask").

What would be the most precise way to do this?

I thought about using "方がいいのだ" but it struck me being a simple suggestion, while I'm looking to put the emphasis on the necessity of taking the action given circumstances. I thought of using "必要がある" where 必要 (noun/na-adj meaning "necessity"/"necessary") acts as the sentence subject, taking the "strongly advisable action" as its description.

There's also 余儀なくされる, which is a pretty particular verb meaning:

to be forced to do or experience something (against one's will); to be forced to do something because one has no other choice

Which I thought could probably be used with verbs in te-form or with the stems themselves, but it is a verb I have never seen before, and does seem to carry the nuance of having actual serious consequences for not doing the expected action.

Answer 1

I would use ないといけない or its shortened colloquial version ないと.

彼女に電話して教えてあげないと。
I have to call her to let her know.

ないといけない sounds less obligatory and more subjective than なければならない, while the latter’s contracted colloquial form なきゃ can be used practically interchangeably with ないと.

彼女に電話して教えてあげなきゃ。

As a native speaker of a Western dialect, I personally never say なきゃ even when I'm speaking in standard Japanese (perhaps unless it is followed by いけない) because it sounds feminine to me. I guess it is a regional thing.