DIY ammo for MAKE issue #2′s Marshmallow gun Howtoon! Marshmallows are spongy confections made of sugar beaten into a fluffy texture with the aid of gelatin. Marshmallows are essential components to many popular American snacks such as Rice Krispies Treats and S’mores (a sandwich of graham crackers, chocolate, and marshmallows melted over a campfire) Link.