For native apps, you can delete the app icon from Apple Menu bar by holding the Command key and dragging it off. Or, you can remove the app icon via System Preferences. For third-party apps, you can remove the app icon by stopping it from working in Activity Monitor.
To remove native apps from Apple Menu bar:
Option 1. Use keyboard and mouse combinations.
Step 1. Press and hold the Command key.
Step 2. Remove a menu bar icon by clicking and holding it, then dragging it off of the menu bar.
Step 3. Once you see the X symbol, let go of the mouse.
Unfortunately, this method doesn't apply to Siri or Clock.
Option2. Delete app icons from System Preferences.
Step 1. Click on the Apple menu from the top-left corner, then choose System Preferences.
Step 2. In the System Preferences panel, click Control Center.
Step 3. To remove an item from the menu bar on your Mac, find the app and choose the Don't Show in Menu Bar option next to it.
To remove third-party apps from Apple Menu bar:
One strange thing reported by users on the forum is that the app icons remain in the Apple Menu bar even after uninstalling apps on Mac. Possibly, the app is still running behind the scene with leftovers of it. To get rid of the app icon, do the following:
Step 1. Navigate to Applications > Utilities > Activity Monitor.
Step 2. Search for the program you want to remove from the Menu Bar.
Step 3. Tap on the Memory section from the top-right menu.
Step 4. Find the app then select Stop, which is shown as the X sign at the top.
In this case, the app icon should disappear from the Apple menu.