This is a simple print for sprouting lids on a mason jar. I have included wide mouth and standard mouth lids. 
To print these successfully you have to set the top and bottom layers to zero. I have included the gcodes for PETG. I choose 40% infill but you can increase or decrease as you like. I felt that was a good all around size for whatever I might want to sprout.

1. What are sprouting lid for?
They are for sprouting seeds, or nuts, legumes or grains.
You can take them and plant them, if you're using them to start a garden. You can also use them for food. If you want to make rejuvelac for making cultured tofu or yogurt. Often to make beer you'll use malted barely, aka sprouted barely.
2. How do you use them?
Replace the regular lid with the sprouting lid. That's it.
Fill the jar with your medium and put the sprouting lid in the metal ring and screw the ring onto the jar.
Rinse your medium. Then fill the jar with water to the top. 
Let them soak over night, or 8 to 10 hours. I suggest 1 cup of seeds for a quart size jar. They will expand quite a bit after soaking.
After soaking empty the water and rinse the medium then drain.
Find a container or bowl that can hold your jar at an angle upside down. This will help drain more of the water. Keep it in the container upside down and cover it with a dark towel and leave it over night, or until you start to see sprouts coming. It should only take a day or 2.
If it takes longer than a day, be sure to rinse the medium daily and put it back in the upside down position in your container and keep it covered.
After you have sprouts you can remove the cover. Plant them into your containers or the ground.

To make rejuvelac there's one more step. After they have sprouted fill the jar with water again and let it ferment for about a day or 2. You'll see bubbles in the water, then you'll know it's ready.

Here's an amazing video on how to do this and make chickpea cultured tofu and yogurt. This is actually where I learned about this technique. All credit goes to Gourmet Vegetarian Kitchen. :-)
https://youtu.be/rxyDMb6SMiE