Which do you think?
Both!
It depends on if you are using “hole” to refer to the number of openings, or the topological shape of the straw.
One. If you were starting from a solid piece of material, you could make a straw by drilling a single hole all the way through.
One long hole
Two. Only a person who thinks his lips and his anus are the same thing could think otherwise.
Or you could start with a donut shaped piece of plastic and stretch it out to make a straw. Still only one hole.
Both. You could say there’s a hole in one end, and flip it over and say there’s a hole in the other end. And entrance and an exit, say. We do this with tunnels. Or really anything. Your home has a front door and a back door rather than a single “opening”, despite there being an unbroken path from one to the other. Your anus and mouth are usually considered two openings, rather than one, even though they are connected.
Topologically, it’s a single hole. Human language usually doesn’t adhere to mathematical rigor, though.
One hole, two openings
However, water is definitely wet.
Other than an excavation or depression like a hole in the ground, the common definition of a hole is an opening through something. If a straw has two holes, then so does any object with a hole in it. Would anyone say that a donut has two holes?
This. Its basically the standard I’ve always used in reference to any tubular object.
If Homer digs a hole in the ground in Springfield, and Wong digs a hole in the ground in China, is there one hole or two? If they keep digging until they meet in the middle of the Earth, one hole or two?
It’s one, but I call it two.
It’s a genus-1 surface. So one hole.
It does have 2 ends. But ends and holes are different things.
If it has two holes, where does one hole end and the other begin? Is there a magic place in the middle of the straw where holes touch?
If you drill a hole through a board are you actually drilling two holes?
Does this mean we should stop saying “wormhole” and say “wormholes” instead?
I’ll tell you after I put on my pants.
^This. A straw with one hole is a cup. A very skinny cup.
We’ve seen plenty of examples 'round here that prove that the asshole and the mouth are pretty much the same, judging from the things they say. 
This caused two of my co-workers to very nearly spray coffee all over their keyboards when I read it aloud. Well Done!
One hole, two ends.
What about a straw with no holes? :eek: A thermos that cannot be opened?