I train in the early morning, 5 am or so, at times. I don't eat before training but I use a zip lock bag, one that has a real zipper, and put my protein powder and some weight gainer in it with a straw. I carry that in my gym bag for after my workout. After my workout I take out the straw and put some warm water into the baggie. Shake it up and stick in the straw and drink it. When I'm done I throw the bag into the trash. Quick and easy with no mess to clean up later.