What I found was that the barium drink went straight through me! It's a good thing I always carry spare supplies with me, as I filled up 3 or 4 pouches in the 30 minutes between the time I drank it and getting the test! (In fact, that's the reason I increased the number of spare pouches I carry with me.) Just let the testing personnel know that this is a possible side effect.
I have always advocated carrying spare supplies in an inconspicuous manner. It is much easier for women than men, of course, as nobody thinks twice about a woman carrying a purse. But my spare supplies are all packed into a small pouch - a former contact lens supply kit about 6"x4.5"x2.5" - not really very large at all. It contains 5 or 6 pouches (disposables) with disposal bags, one faceplate, a template for cutting out the stoma-shaped hole, a Sharpie marker for marking the faceplate and scissors to cut it, and miscellaneous stuff like a few wet wipes, Band-aids, etc. Everything you could conceivably need in a tiny package.