I have tried similarly using a plastic skipping tube (not hollow). i heated the end to make it smooth and tapered. I inserted 2 meter long tube into my bladder.
Thanks... I made this one with 7/16 vinyl tubing and an end cap glued on the end. The tube had to be heated to change bring the size down a bit to fit the cap, giving it a tapered size. The cap was bought from a radio shop. It was designed to go on an antenna. I wouldn't recommend doing this without being sure the cap is well glued on the tube....lol I put a glow stick in for effect and perspective. The vinyl is a nice slick surface and a little lube makes the stretch easy. I have a bigger one at 1/2 inch. The upload should be available in a day or so. these go all the way to the bladder.
How long is it?