How to transfer fuel without docking?

[LUIS94]

It's possible?

[Halliwax]

Between two vessels? How else would you do it, teleportation? No, you need to dock.

[Chibbity]

You can use the KLAW if you don't have docking ports.

[Jupiter3927]

Your two vessels have to be docked to transfer fuel between them.
The only way around this is by using a dedicated fuel vessel to dock to one ship and move the fuel to the other.

The klaw can transfer fuel only if you have fuel crossfeed rules disabled in the difficulty settings.
Klaw grabbing is still basically docking but with more flexibility and your vessels still need to be gently rammed into each other.

[GunsForBucks]

You could <or used to be able to> use a small fuel tank and connect it in eva construction mode.
You could then transfer fuel and remove the tank and put it back in storage where it would refill. Take a bloody long time to fill up a big tank with a tiny one though.
Probably easier to throw the grabber claw thing on it in eva mode and dock, then remove it when done if you don't want to leave it there.

[Tsparksmlp]

Yes you need Kerbal attachment system you can use the resource transfer station.

[XLjedi]

You could fly the fuel tank between vessels I s'pose?