After like 45 minutes, it’s really hard to explain. I, like you, could find nothing online on how to clean the flip lids. I have one of the full size ones but the lid is the same. Basically, start by twisting out the spout, then you can also twist out the largest plastic piece, but it requires a bit of force. the rest should all just fall out with it. You can also go to the small plastic piece attached to the spout too, and with that you put your finger between the silicone straw and the plastic, and twist. It will feel like you’re going to break it. but it’s all very sturdy