USGI canteen and canteen cup are my backup.
Unless I'm bringing the Svea-123. In which case I have a 1.5L aluminum pot that it rides in. The top, w/folding handle, is also a fry pan/ lid/ bowl/ wide cup.
Depending on the situation a 20oz wide-mouth insulated plastic mug, $4 with a coffee fill at a gas station, gets a lot of use. You can't heat anything in it but you can pour in boiling water and stuff will cook/soak/hydrate. Works great for drinks like coffee or coco, oatmeal, dehydrated stuff.
I have been known to assemble a "hobo" cookware set, a one or two pound coffee can (depends on how many people and how much cooking we are planning on) and one or two soup cans for cups. Stiff wire, I have used bicycle spokes, #10 copper or galvanized 'nine wire' to form handles and hangers. After a weeks use they can burn thin and need replacing but they are cheap and easy to make. Thicker copper wire fittings can often be reused several times.