I'm going to be moving most of the GorillaBlues into cups tonight and I wanted to show the Hempy cup. These little cups put in a ton of work for me. They have housed mothers and fathers for months without a transplant.
Any 12oz plastic cup works. Here I used a red solo cup and a 5/16 Allen wrench to make the drain hole. I just heated it up and it melted the opening. I centered it at 1-1/2 inches up from the bottom of the cup to give a couple of ounces in the reservoir at the bottom:
The key to keeping plants in this small container is multi feeding. Once the roots start to become rootbound I increase feedings to keep the medium moist so I salts don't build up and cause issues. The mini-reservoir on the bottom of the cup keeps the root zone moist between feedings and acts as a buffer during the plants growth cycle.
For me, I am using nothing but perlite as the medium and I am feeding every 24 hours till I get an ounce or two of runoff out the drain hole.
Very similar to growing with coco and is a great way to utilize a small space.