Whole Milk- best for thick and rich foam. Soy Milk- adds a milk tasting and lactose free foam. Coconut Milk- best for saving a few calories and has a nice flavor. Oat Milk-great for a lactose-free option. Skim Milk- best for lighter and easier frothing. Almond Milk-smaller foam bubbles and doesn't require high temp heat to foam. Heavy cream- creates an extra thick and rich topping.