...also no need cycle. (it the same water, still has healthy bacteria, no?)
Still has healthy bacteria? No...
The good bacteria that you need and want are not floating around in your tank like noodles in soup or ice cubes in a pitcher; they are sessile and live on surfaces in your tank, especially in the moving aerated water in your filter. You can literally change all the water in your tank, every day, without affecting those bacteria...as long as the new water you put in has been dechlorinated and is at the right temperature. Most of my water changes involve removing almost all the water, leaving enough in which the fish can splash around at the bottom for a few minutes until I refill.
Cycling the tank doesn't even enter this discussion; this is super-basic Biofiltration 101 stuff...yet a disturbing number of aquarists don't seem to "get it".
So, if I am stuck in the situation which you describe...i.e. a sudden need to empty a tank for some type of maintenance or other reason...I just look upon it as a chance for another water change. I'd put the fish into a temporary home, or another aquarium if available, but all the rest of the water would go to water the garden, or top up an outside pond during a dry spell...in other words, to waste.
If you absolutely must save and re-use dirty water, any kind of clean storage bin or plastic garbage can would work. For greater quantities, maybe a couple 55-gallon food-grade plastic barrels? Even a series of 5-gallon plastic covered pails, sometimes available cheaply from restaurants who buy items like pickles, etc. in them. My personal viewpoint is that if water were so expensive locally that I needed to think about saving and re-using aquarium water, I would probably be raising desert reptiles or growing cactus rather than keeping fish.