many people use the ones that are intended as water and food bowls for dogs and cats. they are cheap, big, easy to clean, and dont tip over easily. you can get them in stainless steel or plastic or stoneware, most are durable enough for the dishwashing machine.

some people also use these thin plastic deli-cups and throw them away after use. im no fan of that because of the plastic waste it generates. i would rather get a few that are basically indestructible and that can go in the dishwasher.