I experimented with doing some Little Gem romaine lettuce and dwarf Toy Choi in plastic window boxes on the front porch this spring. It worked well enough that I'll be doing more this fall once it cools off a tad and this time make sure some succession planting gets done.
Little Gem in April:
Toy Choi in the growing stage:
The Toy Choi was grown as part of table centerpieces for St. Patrick's day and the leftovers were put in a windowbox. It worked well! But I think they could probably grow to maturity in the cups as shown without too much problem. By the time they get rootbound they will have been consumed.