This achievement is no longer bugged!
A simple way to ensure you meet the 100 meters from a single toss is to build a large tower. I always build a tower that goes to maximum height (with a small pool at the base for some fun jumps).
Basically just get to the top of the world and aim out in any direction and throw the Ender Pearl as far as you can.
Make sure you don't aim too high or too low, or you won't travel as far as you need to. Try to give it a good lob to get the most distance you can.
When you land, if you traveled far enough, the achievement should unlock!