This fast food cup illusion is really confusing the internet

There's only one thing Twitter loves more than a rage-fuelled political debate, and that's a good mystery.

On Sunday, Twitter user @franco_713 shared a video of himself pouring soda between three different-sized Jack's fast food cups.

"They rlly be finessing our ass lmaoo," he wrote alongside the clip.

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The obvious implication is that we're getting the same amount of liquid no matter what size cup is purchased. But is everything as it seems?

Unsurprisingly, the people of Twitter were skeptical.

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@franco_713 was undeterred, though. In response to the request to pour the liquid in reverse, he shared a second clip:

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Still: not everyone was convinced.

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Once again, though, @franco_713 replied.

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So what's actually going on here? Do the cups really hold the same quantity of liquid, or is there some clever trick that's being played on us?

Mashable reached out to Jack's about the video and we will update this article if we receive a response, but in the meantime there are still some unanswered questions and things to bear in mind.

In the first video he spills some liquid, first of all, and it's possible -- as people pointed out -- that there could already be liquid at the bottom of the bigger cups.

And in the second two videos, he doesn't show all of the bigger cup in shot as he's doing the pouring -- which means it could have something in the bottom of it that's reducing the quantity of liquid it's holding.

The mystery continues...