A few options exist.
Pouring the bleach in the hose is the simplest and also helps sterilize the hose, always a decent idea. Wear old clothes; don't ask me how I know to suggest this. Full strength bleach is possibly hard on the hose and seals etc., but it doesn't stay in contact with them for long enough to be a worry (it gets quickly flushed out when you subsequently fill the tank).
If you have a winterize suction line connection, you can set the valves for winterizing and open the fill valve and the pump will suck the bleach solution from a bucket or whatever via the winterize hose and put it into the tank. This can also be used to fill the tank from a portable container should the need come up.
You can also use an external pump or siphon from sufficient elevation to provide enough pressure to get past the check valve in the water inlet.