Without fluid friction, all objects accelerate at?

Explanation:

When an object moves through a fluid, like air, water or oil, the object experiences a resistance to flow; this is, to pass through the fluid.

This resistance force is the fluid friction.

In few words, fluid friction is a force that opposes the motion of the objects through the fluid.

Then, in the abscence of fluid friction, all objects falling accelerate at the gravity acceleration.