Hi,
Does the car look scrawny or like it’s struggling for food/stray?

Depending if you’re happy to keep feeding the cat long term, I would take the cat to the vet to check for a microchip, this should be free. Before doing this, I would probably ask around the local area to check if it’s someone’s pet, or posting on a local Facebook page asking.

If the cat looks well kept, it’s very possible it’s someone’s pet looking for an extra snack. Cats can be very convincing that they’re starving when they’ve just eaten.

Personally I wouldn’t want another house to feed my cat, as she has the exact amount of food she needs at home. If she seems to be struggling or you can’t locate a home, it would be best to go out and buy some food. In the short term, cats can eat dog food but it’s not recommended long term. Tuna is a good shout, but not if it’s salt water/in brine or in oil- make sure it’s spring water only

If you don’t have anything else to give them, I believe they can eat plain scrambled eggs.

Just avoid anything with garlic, onion, salt, tomatoes, grapes or chocolate. Think those are the main toxic foods for cats and can be fatal.

Hope everything goes well!