Answer by
LeheckaG (1826)
Gasoline-siphon?
You can get inexpensive-gasoline-pump/siphons from discount/dollar-stores.
Failing that:
Get a long-length of clear (organic-solvent-resistant) hose/tubing,
While holding (1)end, submerge the other-end & as-much-hose-as-you-can in the-full-tank,
Seal (with your-thumb) the end which you are holding,
Then slowly draw some-excess-slack-hose from the full-tank until you see liquid;
Bend the liquid-filled-hose downward toward your empty-smaller-tank,
release your-thumb & let gravity/suction do-the-work.