{
  "name": "Drink Water Event Popup",
...
  "permissions": [
    "notifications",
  ],
...
}

chrome.alarms.onAlarm.addListener(() => {
  chrome.action.setBadgeText({ text: '' });
  chrome.notifications.create({
    type: 'basic',
    iconUrl: 'stay_hydrated.png',
    title: 'Time to Hydrate',
    message: "Everyday I'm Guzzlin'!",
    buttons: [{ title: 'Keep it Flowing.' }],
    priority: 0
  });
});