Do you ever think about how straws work?
I mean really, really thought about it? The physics, the dynamics?
The liquid in your cup has weight to it, it produces pressure. Not, you know, a lot, but pressure. Down near the bottom of the cup(where the end of the straw is) you have more pressure than near the top. The air around you is also putting pressure on the liquid. With nothing acting on it, the pressure inside the straw is the same as the pressure outside, so the fluid level inside stays the same as the rest of the drink.
When you put your lips over the straw and suck, you are reducing the pressure inside the stray. this causes the air pressure outside to literally push the sugary sweet drink up into your mouth! The more liquid you remove from the drink, the lower the pressure it exerts, and the harder it gets to suck the liquid up.
Its the sort of common, simple, every-day thing that most people take for granted. You don't even consider the forces at play. But really, its far more complex than you realize.
And this, my friends, is what you have to consider when writing. This level of complexity. That doesn't mean you have to write about it, but just be aware: nothing is as simple and mundane as it seems.