The food items swear so much because the employees do it so casually. They probably just think that's how people normally speak.
Douche starts killing and drinking liquor bottles after sucking dry a damaged box of grape juice. Since the grape juice had been in that state well before the plot started, he'd most likely fermented into a cheap wine.
The extreme preoccupation with sex demonstrated by pretty much every significant character makes more sense if you consider that their actual function as food products is to satisfy basic biological urges. They have no need or inclination to ingest anything themselves - indeed, it took Douche nearly "bleeding" to death for him to even realize it was possible to do such a thing - but the built-in subconscious urge (death wish?) to slake physical appetite is still there. So in the absence of an instinct to eat or drink, they can't help but heed the equally-primal yearning for sex, or (in the immortals' case) the addict's urge to get stoned.
With weed being a plant, wouldn't they be smoking living beings? Therefore, making them worse than the humans due to BURNING THE WEED AND INHALING THEIR REMAINS!?
The bath salts didn't exhibit any signs of sentience or protest their molten demise, so possibly illegal stimulants are exempt on the grounds that they're not a commercial product.
If all food is sentient in this film, what about food made from food, like stew or bagged salad mix? Would they have multiple consciences? Or would they be a fusion of dead food parts?
That cookbook illustration which Frank uses to try to shock sense into the other groceries could have been even worse, if you think about it. At least the hot dog and the bun it lay in were lucky enough to have each other to cling to, albeit in terror, when their doom was upon them: after all, very few people eat cold, uncooked hot dogs for July 4th. By rights, the sausage should have been charcoal-grilled alive before being placed into the bun, adding grief for her tortured-to-death lover and forced necrophilia to the horrors which the latter would've endured, as she met her own demise.
The animate objects appear to be all things to are consumed.
Does that imply that prescription medications are faced with a similar ugly fate, albeit perhaps less gruesomely as they're usually swallowed whole and not cooked first?
Did none of the supermarket employees ever purchase and consume any of the food while on the job?
Not outside the break room, apparently.
For that matter, how come the products never caught sight of somebody taste-testing a grape from a bunch of them on the sly, or a bratty toddler stuffing an unpaid-for candy into his or her mouth when the adults aren't looking?
It's possible they never associated anything that happened inside the store with the great beyond. Every human is considered a God, and they're used to the Dark Lord picking off random food items. They probably just assumed it was karmic punishment to go out like that as opposed to making it to the great beyond. When all the humans freaked, it was like the gods turning on them en mass.