While in Ultra Space, full heals do not heal any Pokémon with the sleep status. The game claims it has no effect and they are still asleep on the field.
In battle (after using a full heal) will say "<Pokémon> is drowsy!" after the attack (Or failure of attack) and it is suddenly not asleep. I am unsure if this is a mix-up with the drowsy vs asleep status conditions.

The Plants in Ultra Space grant the Drowsy Status, rather than Sleep. That being said, there are a bunch of issues regarding Drowsy and Full Heals, which I will send to our internal tracker. Thank you for the report.