Water:
Most lost birds are hungry and thirsty. Water is necessary before all else. Since pigeons drink by suction, any water container should be at least 1 in. (2.5 cm) deep. An open container, i.e., a dish, an old margarine container tub, etc., is best. While a thirsty bird may drink immediately, it also may not. A bird which has gone without water for a while is sometimes a bit less than itself. It may be so exhausted, it doesn't even realize that water is in front of it, especially if the water
container you use is different from what it is familiar with. A trick I've often used is to trickle a f ew drops of water from on high into the container to make a splashing sound. When they hear that, most birds will invariably head to drink. If a bird looks really exhausted, Gatorade or other proprietary sports drink may be added to the water. A teaspoon or two per cup (250 ml) of water will help replenish electrolytes.

Food:
Pigeons are grain eaters. While park pigeons will eat bread, most domestic birds have been raised on a multi-grain mixture and have never seen a slice of it. In fact, they would likely ignore it as possible food. Instead of bread, you might try feeding them something else from around the house. Popcorn (maize), rice, split peas, barley, buckwheat (kasha), canary seed, etc., are all good first options to feed a lost bird with.

THESE GRAINS SHOULD NOT BE COOKED OR POPPED BUT FED RAW.
Water should also be provided since pigeons normally drink immediately after eating.

What Should I Keep It In?

Any container that a dog or cat can't get into will be fine. An old bird cage will hold the pigeon for a day or so with no problem, as will a cardboard box - a screen on top of such a box is better than simply closing the flaps since there will then be enough light for the bird to see to eat and drink.

Finding the bird's owner.If the bird has a band on its leg, the owner can sometimes be traced through one of the national pigeon organizations. However, this is often not even necessary.
After twenty-four to forty-eight hours rest with food and water, most homing pigeons are more than capable of finding their way home on their own. Simply release the bird in an area free of wires or other obstacles and it will usually head home immediately.
NEVER try to attach a note to the owner by rubber banding it to he bird's leg. This merely cuts off the leg's blood circulation and often leads to gangrene and amputation of the limb. If you do want to attach a small note, tie it carefully to the middle two tail feathers.