If physics simulating you can GetLinearVelocity and multiply that by a number between 0 amd 1 like 0.1 every tick, but only for two of the axes, and just feed the original back in when you call a SetLinearVelocity in the same function.
If not physics simulating you can do likewise but use Get Velocity and Set Velocity instead.
Not sure how clean or realistic or problematic this approach is but try it and and let me know.
Oh yeah and mult by deltatime too because you dont want framerate messing it up.