After you eat a meal it takes around 4 to 5 hours for your stomach to digest the food and empty your stomach completely.
Your stomach should be nearly empty after a few hours but for your stomach to be fully empty after eating a large meal it takes at least 5 hours.
If you need to take medications on an empty stomach and you've eaten you can take the medications after 2 hours when your stomach is almost empty.
The less you eat the less time it takes for your stomach to empty out fully and the more food you eat the longer it takes for an empty stomach.
If you just ate a snack or drank something then your stomach should empty within a few hours or less.