One summer at the De Anza College swimming pool a swim class did the usual work at improving their strokes, building speed and endurance, and . . . trying to learn how to blow big bubbles in the shape of a donut, such as those created by their classmate.
How to blow bubble rings, by Janele Griffith.
First make an O with your lips. Make your lips hard as if you’re pinching them together as if you are angry.
Stick your tongue straight out in between the lips making sure your tongue is hard, then puff up your mouth and cheeks with air. Then blow hard and pull your tongue back into your mouth letting out a bubble with a hole.
You can do the same thing, not sticking your tongue out, but keeping lips in an O and blowing out.