After you eat food the food then goes through a digestion process and the food can stay in your stomach for around 2 to 3 hours before it's completely digested.
Then after the food gets digested the food then is used for energy to provide your body with energy.
The food is fuel for our bodies.
Then whatever waste is leftover from the food that our bodies does not fully use then it goes through your intestines and colon.
Then eventually within 8 to 10 hours or even 24 hours you may need to poop it out.
Just like with drinks your body uses that fluid and then whatever is left goes through your kidneys which filters out waste and then the pee goes into your bladder which is waste products.
But your stomach should fully be empty within 15 to 24 hours depending on how much food you've eaten.