Ensure all ingredients are cold from the fridge.
Combine milk, Greek yogurt, vanilla extract, and sweetener in a small jar.
Seal the jar tightly and shake vigorously for about 1 minute until thickened.
For extra froth, use a handheld frother for 30-45 seconds, keeping it near the top of the liquid.
If using flavor add-ins like pumpkin puree, gently fold them in now.
Spoon the foam over your coffee or cold brew and enjoy!