Gasses don't get "pulled", they get "pushed".
When you empty a neon tube, you attach a device with almost no air in it to mouth of the tube.
The air that is in the tube then pushes itself into the device until the pressure is the same in both.
Meanwhile, the device expels its air to produce more low pressure, and more of the relatively higher pressure in the tube pushes more of its air into the device.
This continues, with the contained air pressure becoming less and less until you decide "good enough" or the limit of the device is reached.
It won't be a perfect vacuum, but it might have say a 99% vacuum, containing 1% of the original air content in the same volume.
For the drinking straw, again it isn't your mouth (the vacuum) that pulls, the liquid actually gets pushed up the straw.
What happens is that the weight of the atmosphere pushes down on the surface of the drink in the glass, and since that pressure is greater than the pressure of the partial vacuum you have created at the other end of the straw, the liquid is pushed up through the straw.
This is much like the way toothpaste is pushed out of its tube.
Similarly, a hand pump on a well works by producing a partial vacuum at the top of the pipe and allowing atmospheric pressure to push the water up the pipe.
There is a limit though.
The weight of the atmosphere won't push the water any higher than about 10 metres (11 yards).
In the case of a straw sealed at one end, suppose that it is made of steel or very strong glass so that it won't collapse, and that it is long and thin enough that bubbles of air won't flow from one end to the other.
The molecules in the liquid are attracted to each other, so the liquid will tend to act like a solid plug.
If a vacuum is applied to the other end, because there isn't any air pressure at the sealed end, no matter how good the vacuum you create at the mouth end, there won't be any pressure to push the liquid plug out.
However, if there is a small pocket of air at the sealed end, then the partial vacuum at the mouth end will cause some of the liquid to be pushed out.
The small pocket will become a larger pocket, but with lower pressure.
This will continue until the pocket's air pressure is equal to the pressure of the partial vacuum you are applying to the mouth, which could happen either before or after all the liquid has been removed.
Remember, gasses don't get "pulled", they get "pushed".
Even when you use a vacuum cleaner to clean a floor, the vacuum doesn't actually suck up the dust.
Instead, the machine creates a volume of low pressure in its canister, and the air in the room gets pushed into the pipe by atmospheric pressure in order to fill that void, dragging the dust along with it.
The best way to visualize the behaviour of gasses is to imagine a room containing thousands of ping pong balls that continue bouncing forever.
- Temperature: the hotter the gas is, the faster the balls will move around.
- Pressure: each ball bounces off a wall by pushing against it, faster moving balls pushing harder than slower moving balls.
- Volume: the larger the room, the longer it will take for a ball to make the next bounce off a wall, and so fewer bounces will happen in a given time interval.
If a wall is moved outward to make a larger room, there will be a brief period when there are no balls near it (a vacuum), but the balls will quickly fill that space and the larger room will soon reach equilibrium again.
The wall didn't "pull" on the ping pong balls, it simply created a void where the balls were "pushed" into.
Meanwhile the larger room means less frequent bounces, which means less pressure.