You could cut a hole in the cap big enough to fit a stopper. Put a small amount of silicone around the mouth, then screw the aluminum cap on that to seal it.
You'll have to re-seal it if you open it but doing a cider it should be a while before you have to open it again.
Beer, happy Produce of our Isle/Can sinewy Strength impart,
And wearied with Fatigue and Toil/Can cheer each manly Heart.
Labour and Art upheld by Thee/Successfully advance,
We quaff Thy balmy Juice with Glee/And Water leave to France.
Genius of Health, thy grateful Taste/Rivals the Cup of Jove,
And warms each English generous Breast/With Liberty and Love!
(Rev James Townley, 1751)