Beat eggs in a medium bowl until yellow and frothy. Add garlic, salt, and pepper.
Toss spinach, Muenster cheese, and onion together in a small bowl. Divide evenly among the cavities of a silicone egg mold. Pour beaten eggs into each cavity, filling each 3/4 full. Cover mold with aluminum foil.
Pour 1/2 cup water into a multi functional pressure cooker, such as Instant Pot. Place egg mold inside. Close and lock the lid, sealing the vent. Select Steam function; set timer for 13 minutes.
Release pressure naturally according to manufacturer's instructions, 10 to 40 minutes.
Instant Pot Egg Bites · Dinner Match Lab | Dinner Match Lab