Quick Cloth Inflate is an addon to create inflated objects quickly.

How to install

install directly from the ZIP file, no need to extract the content.

How to use

1. Select your object or create a cube and subdivide it five times to get a high dense mesh.
2. Create a collision object such as a plane and make it "collision" in the physics tab.
3. Go to the "N" layout panel and select the cube, click on "Inflate Now", this will make your object have the pressure settings in order to inflate it.
4. Play the animation on the timeline.

To consider:

This addon uses the default Blender cloth settings but with different Pressure values, this means you'll see the cloth panel visible on your physics tab.