The Force struck early in Fiji via outside centre Sio Tomkinson to take a 7-0 lead in Saturday's Super Rugby Pacific match played in hot and humid conditions.
But Drua piled on the next 38 points in the five-tries-to-one romp to make it nine consecutive victories at their home fortress of Churchill Park.
The result left the Force (22 points) in ninth spot, meaning even if they beat the NSW Waratahs in their final match of the season next week, it won't be enough to secure a top-six berth.
Drua (20) got off the bottom of the ladder with the bonus-point win, with the wooden spoon battle now between the Drua, Force and Highlanders (19).
The Force's hectic travel schedule meant they entered the match without rested Wallabies trio Nic White, Hamish Stewart and Harry Potter.
With Nick Champion de Crespigny (concussion) and try-scoring machine Carlo Tizzano (pectoral) also unavailable - and star flyhalf Ben Donaldson starting on the bench to manage his minutes - the Force were missing more than a third of their best starting XV.
Fijian Drua capitalised on the Force's numerous handling errors and missed tackles, with Elia Canakaivata crossing for two tries in the second half as the visitors tired.
The fatigue was no surprise for a Force outfit that will have travelled a whopping 49,050km for the season by the time they return to Perth this weekend.
Coach Simon Cron hit out at the criss-cross nature of the Force's fixture, with their tired display in Fiji further evidence of the toll it has taken.
The Force haven't won outside of Australia since round 15, 2022, and their latest defeat was another demoralising reminder about the gap that still needs to be breached to become a genuine finals threat.
"I thought we started really well and then they gained the momentum and we couldn't get it back," Force captain Jeremy Williams told Stan Sport.
"(We had) poor discipline and we turned the ball over too easily.
"It's the second week in a row we've done those things. Against a quality side like the Drua, you're going to pay."
A wayward pass from the Drua gifted the Force the opening try in the third minute, with scrumhalf Henry Robertson breaking a tackle in the counter-attack before offloading for Tomkinson to go over.
That was as good as it got for the visitors.
The Force held firm for the 10-minute period Robertson was off the ground for a yellow card.
But the Drua were able to strike in the 29th minute when a brilliant pass while being tackled to the ground by Iosefo Masi helped gift Philip Baselala a try.
And when the Force failed to deal with a short chip over the top in the 36th minute, Masi pounced for a try to help extend the margin to 17-7 by halftime.
The second half was all one-way traffic.
No.8 Canakaivata twice busted through the Force wall on the line to crash over.
And the bonus point was safe when Selestino Ravutaumada chased a long kick down the field and got the ball from a frenetic breakdown to touch down in the 72nd minute.
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