The Apple symbol () is not available on the touch keyboard in iOS. If you use an external hardware keyboard you can easily write it with the keyboard shortcut ⌥ A.
To write it on the touch keyboard you have to create a text replacement. Go to Settings > General > Keyboards > Text Replacement. Tap the plus sign top right to create a new text replacement. Copy and paste this into the Phrase field and choose what you want to write that is replaced by in the Shortcut field. Don't forget to save.
