I never tried a long term test to see if they really lasted forever, I just observed that they had no spoil timer in the fridge. If you take something out of the fridge and set it elsewhere, or put in in your inventory, it will get a spoil timer based on it not being refrigerated. I guess it's possible that there is a hidden long term timer while they are in the fridge, and once that finally gets under a week it will finally show.
20 days without spoiling is still really great for a sim running a yard sale.
I can't see any benefit to selling juices from a food stand instead of vendor table.
When I tried selling a 12-pack from a food stand, sims were buying one can at a time instead of the whole pack. Not efficient at all!
I finished play-testing yesterday to choose what juices a future sim will be selling, but I'll check vendor table spoilage using a debug item later today.
Question for you: Do you use juices for emotional moods? Your explanation of how Tofizz works to cancel juice moodlets makes juices a contender.
But I'm lazy and prefer emotion berries, club vibes, and incense burners.