Filling void under concrete

[Pulleye16]

I have a couple voids from washout that I'd like to fill before they become unrepairable.

I have a small void that tucks under my concrete floor in my garage and another small void/hole under my apron by my other garage (not related). I fixed the drainage direction already, now i just need to fix/fill the hole.

Are there any DIY solutions? the concrete has not settled or sunk so I don't need to jack it up any...I just want to fill the hole.   

Only thing I've seen online that "I" can do is use expanding foam...which I'd rather not. Can I just mix up some concrete (soupy) and fill the holes that way? what problems would that cause if any? The one on the apron is fairly small but the one under the garage is unknown but from what I can see, doesn't look to large.

If I have to go foam, I will I guess but would rather use some type of concrete.

Thanks!

[LPS]

The soupy concrete to flow in sounds like a good plan.  ???