Turns out it was FOOF.

Opportunistic Lab Intern:

“While you’re all debating if it’s half full or half empty I drank it. Now it’s empty.”

Engineer: The glass is twice as big as it needs to be.

Obligatory xkcd

The beaker is always full, when it's half full of water, it is also at the same time half full of air. THE GLASS IS ALWAYS FULL

Realist: who’s cleaning all these glasses?

My mother in-law is a lab scientist. She says this is accurate.

Ah, it's this time of the year again. (version 3)

My lab is pretty easy to guess, it's either 18 MΩ water, 100% EtOH, or 16M HNO3. 66% chance it's not acutely dangerous, not bad for a lab!

Scientist Russian Roulette: Drink the mystery breaker. They all have water, except for one that's hydroflouric acid.

Ahh found that label!:

99.985% Pure.

Nitrogen (N₂): 39%

Oxygen (O₂): 10.5%

Argon (Ar): 0.465%

Carbon dioxide (CO₂): 0.02%

Water (H₂O): 50%

I thought the half full, half empty thing. Was about the flow of water. If you're emptying the glass, at some point the glass will be half empty. If you fill the glass, at one point the glass will be half full.

100% Full with 50% volume occupied by Dihydrogen monoxide molecules and 50% volume occupied by a mixture of molecules in gas form, colloquially refer as "air", which contains, according to the statistical data recorded by analyzing the gas molecules in the air in the Earth's Atmosphere, 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other trace gases.

🤓

(I have no idea what I'm saying lol)

After a long romp, a fairly new g/f went into my kitchen, grabbed a 1 gal bottle of white vinegar from the fridge, poured herself a glass and tried to chugged it while I was still in bed recovering. -She had the nerve to think I tried to poison her (for half a minute)!

Read and use labels. lol

That beaker does not look half full to me. Many like 1/3rd full, or at least somewhere between that and half full.