Question: I am just curious if last minute hotel deals is actually a thing. I am not a big traveler and have no clue.

But in theory if a hotel has a bunch of empty rooms for the current day, it would make sense to rent them at a reduced rate as opposed to letting them be empty.

Is this actually a thing that could be leveraged?

I am going on a road trip, and the last leg of the trip could take many variations on a moments notice and was wondering if this is something I could take advantage of.

Answer: 
**Yes you can ask.** And **I have successfully asked for extra food in the past** (i.e. over the last five years and as recent as a month ago). One time when asking for a second sandwich I was even proactively offered a third one later on. I also typically ask for two beverages and never had that refused. 

Of course they have no obligation to give you extra food but on a full service airline they are usually happy to. (Since you mention a first meal I assume you are on a full service airline. If you had to pay for your first meal, you'll have to pay for the second as well.)

A good strategy is to **ask when they have just finished distributing meals and you have already finished yours** or if you already know to be hungry, you could tell them **when you get the meal that you would be interested in a second serving.**  

Be nice, don't interrupt and you have good chances.
Airlines: Emirates
Route: Dubai to India (CCU)
Well, I got encouraged by the answers here and asked.
The answer was a "No".

In the airlines defense, I asked for a Hindu meal, which maybe was limited in number.
But, guess what my co-passenger told me.
If you had asked it in your flight from Dubai to some western country they would be more than willing to serve you.

But here you are going back to the third world. You are lucky the "No" was not a rude one.
Ouch... :(