Dry chemical fire extinguishers are really a powder blanket,, they put out fires by covering the fire like a non-flamable blanket. This smothers or starves the fire for air or oxygen..
The bucket of sand will do the same thing, but an extinguisher that could hold all the sand in the bucket would have to be about shoulder high, so it would be difficult or impossible to use..
Plan on using the sand like a hand applied blanket, to cover and smother a fire if needed..
If you wanted to put out the fire in your stove, I doubt that the fire extinguisher could do it.. but if you shoveled or tossed the whole bucket of sand on the fire, it would go out, because no air could get through the bed of coals, it would be sealed on the top with the sand..
Hope this makes sense.