If i have 2 bottles of vitamine pills both almost empty then it would be nice if i could put the pills of bottle 1 in bottle 2 to free up a slot.
Same for water, if i have a canteen with 18% and a water bottle with 33% then it would be nice if i can put the water of the bottle in the canteen or the other way around.
Or from canteen to canteen etc.
This could be done with a lot more products.