Over the years, I've grown quite a few plants in containers without drain holes but currently, I only have one planted like that; a little Hypoestes (Polka Dot Plant) growing in a little plastic juice glass, sitting on my kitchen counter. I like being able to view the roots.
I see it needs to be pinched back again .
I took a cutting of Pachira aquatica last year and rooted it in a glass container without drainage. It was doing really well but when we moved, the container got broken. It was a really busy time so I sat the rootball down into a plastic storage container and just left it; I pour a bit of water over the roots every so often and let it soak in and then pour off any standing water. That plant is still sitting in the plastic bowl 4 months later .... I really need to repot it!