I have always had issues with clumping with water bottles and whatnot. Currently I have one of the generic shakers with oz on one side and ml on the other, with the little grid that goes in at the top. It aerates the shit outta the shake, but it also leaks like a damn sieve. There was a little rubber o-ring that kept it sealed, but that is long since gone. I even cut the rim of the lid down with an exacto knife to improve the seal and that helped quite a bit, but it still leaks. Its kinda awkward when someone comes into my office and I am licking brown fluid off the side of my shaker and sucking it off my fingers.