The Brief: This Twitter meme format uses a broad meaning of "sexual tension" to point out the sexual tension between two or more people and/or things.

DEEP DIVE
“The sexual tension between” memes highlight tension between two or more things, dubbing it as “sexual tension” for a dramatic and comedic effect. Variations of these Twitter memes illustrate both tensions that might normally be called “sexual” and ones that typically wouldn’t be characterized as such.
The sexual tension between you & the person looking at the same painting as you in the art museum
— elizabeth 🦌✨ (@prvserpine) August 18, 2020
According to Know Your Meme, the first known iteration of this joke on Twitter appeared in a 2011 tweet by @_Scottness that read “the sexual tension between you and your yogurt when you forget the spoon.” Over the years, this format evolved to include situations that are tense or emotionally fraught, but not necessarily sexual.
the sexual tension between me and my barber when he spins the chair
— Cryptic (@CrypticNoOne) August 20, 2020
These memes peaked in popularity in August 2020 where multiple iterations received tens and hundreds of thousands of likes on Twitter.
the sexual tension between u and the last breadstick in the basket
— corri (@okiecorri) August 19, 2020
In some cases, these memes highlight everyday situations with unexpected underlying sexual tension.
The sexual tension between you and the person adjusting your seatbelt on a rollercoaster
— 𓅰击Wheat Feild击𓆏 (@wendys_dumpster) August 1, 2020
Some people used the meme format to make political statements…
the sexual tension between duterte and a jail cell 🥵
— matthew deza (@matthewdeza) August 19, 2020
the sexual tension between my lighter and my neighbors trump flag
— kate (@kaiteasley) August 19, 2020
Or to note the wonders of nature…
the sexual tension between the moon and the ocean
— juice🍸 (@SokkaSupreme) August 18, 2020
Staring at the blank page before you, open up the dirty window…
The sexual tension between a writer & the blank google doc staring them in the face as they continue to scroll twitter.
— xαt 🔮 taking a long nap 💤 (@vorejutsu) August 19, 2020
Is she…you know?
the sexual tension between you and the girl commissioned to paint a portrait of you
— river (@ladyonfires) August 17, 2020
the sexual tension between white dudes and drywall
— blm donny (@_donnydrama) August 19, 2020
More generally, this sexual tension meme format can be used to pair any two things that go well together or find themselves intertwined (aka in an entanglement).
the sexual tension between the films in my watchlist and my very short attention span
— khy (@bugdoII) August 19, 2020