Pokémon Sleep 1st Anniversary News: Day 7
Good-Night Ribbons: In early August, you'll be able to place a Good-Night Ribbon on your helper Pokémon to improve their abilities. Pre-evolved Pokémon will also be more effective!

YouTube Clip - Good-Night Ribbon | Pokémon Sleep

Source: https://www.youtube.com/watch?v=PgmmOHmswnI

First Anniversary Announcement Day 7: A New Feature Is Coming Soon—Good-Night Ribbons!

As part of the First Anniversary Fest, we’ve been announcing new information about Pokémon Sleep each day for a week.

Our announcement for day seven is about the new Good-Night Ribbon feature. This new feature is meant to help you feel closer to your helper Pokémon. We plan to add it during an update in early August. Please see below for more details.

What Is a Good-Night Ribbon?

Helper Pokémon can now get Good-Night Ribbons based on the amount of sleeping time you’ve shared.
Note: You can see a Pokémon’s Good-Night Ribbon, along with its effects, and your shared sleep time on the Pokémon’s details screen (from the home screen, tap Pokémon, then Pokémon Box, and then on the individual Pokémon).

Getting a Good-Night Ribbon will raise some of a Pokémon’s helping stats. The effects it has on stats depend on which of four levels of Good-Night Ribbon it is, and these levels are unlocked based on the amount of sleeping time shared with that helper Pokémon.

Also, if you reach the third ribbon level, you’ll get a special profile icon of that Pokémon!

In addition, if that helper Pokémon is still able to evolve, then it will get an additional boost to its helping stats. With the effects of the Good-Night Ribbon, it may be easier to include unevolved Pokémon that couldn’t help much before on your team.
Note: The number of times a Pokémon can evolve depends on which Pokémon are included in Pokémon Sleep.

Good-Night Ribbon Effects

• Ribbon level 1: 200 hours of sleeping time shared
　• Carry limit +1
• Ribbon level 2: 500 hours of sleeping time shared
　• Carry limit +2
　• If the Pokémon can still evolve once (example: Pikachu), its helping frequency is shortened by 5%
　• If the Pokémon can still evolve twice (example: Pichu), its helping frequency is shortened by 11%
• Ribbon level 3: 1,000 hours of sleeping time shared
　• Carry limit +3
　• Special profile icon of that helper Pokémon
• Ribbon level 4: 2,000 hours of sleeping time shared
　• Carry limit +2
　• If the Pokémon can still evolve once (example: Pikachu), its helping frequency is shortened by 7% (for a total of 12% shorter)
　• If the Pokémon can still evolve twice (example: Pichu), its helping frequency is shortened by 14% (for a total of 25% shorter)

Note: Each level’s effects will be added as you unlock them.
Example: If you unlock ribbon level 2 with Pichu (a Pokémon that can still evolve twice), you’ll get the effects of ribbon level 2 in addition to the effects of ribbon level 1.
Therefore, that particular Pokémon will get three effects from the ribbon: +1 to its carry limit from the ribbon level 1 bonus, plus an additional +2 to its carry limit and 11% shorter helping frequency from the ribbon level 2 bonus.

Source: https://www.pokemonsleep.net/en/news/313538303134313434353433343537323831/