I can't find where I had this saved, but I remember this fic very specifically. - Sam and Dean are kidnapped/captured and wake up in an underground bunker-like room with one bed, a toilet, sink, limited canned fruit rations and no way out.

Found in comments! Details contain spoilers / under the cut.

- I remember they're trapped in the space by multiple layers of brick sealing over the entrance.- They try to use the cans to scratch out the mortar before they get too weak to move.- They're forced to share a bed.- Dean takes the smaller of the two bowls without Sam knowing (so that Sam will have more to eat) and Sam gets really mad when he finds out- They plan to die together if they have to (suicide with the sharpened pieces of the cans).- Some workers or something notice Sam tapping in morse code and save them?- They're in the news and they're not the only ones to be kidnapped.- I know this ends in Wincest and they're really clingy after they get saved.- John moves them into a cabin with a big door that opens and they're both really clausterphobic.- John thinks they're too close and is suspicious