Quite literally
Bro took the word "Sandwich" literally
best reply award goes to u
OMG THIS IS THE MOST HILARIOUS REPLY TO A QUESTION I'VE EVER SEEN AHAHAHAHAHAHAHAH
Despite everyone all of you to come here and leave a reply, you still didn't give me reccomendation
Well I have too many polys and I'm too lazy to go through them lmao, you can have a look in my lists if you'd like (if you strictly mean 3p sex scenes I don't remember if there were any in the straight list, while most of the BL ones have at least one scene):
https://www.mangago.zone/home/mangalist/2486827/ (BL)
https://www.mangago.zone/home/mangalist/2375222/ (FL, very few are smut though)
https://www.mangago.zone/home/mangalist/2688301/ (throuples, so basically proper triangles and not 'angles')
Oh I thought u meant like actual sandwich lol, here u go!!
https://www.mangago.zone/read-manga/aisare_neko_wo_hantoubun/
Any sandwich manhwa plz