Food is an artifact type. Even though it appears on some creatures, it's never a creature type.

You can't sacrifice a Food to pay multiple costs. For example, you can't sacrifice a Food token to activate its own ability and also to activate Maraleaf Rider's ability.

Whatever you do, don't eat the delicious cards.

No player may take actions between the time you announce you're activating Witch's Oven's ability and the time you sacrifice a creature. Notably, they can't try to remove or shrink the creature you'd like to bake.