The bug
Right-clicking an area effect cloud with a glass bottle in creative mode gives you a dragon's breath item. Expected would be that you do not get an item, because other actions like the following ones do not give you an additional item.
Right clicking with empty glass bottle on cauldron does not give water bottle
on the other hand ability to pick up buckets was added (see MC-9856)
How to reproduce
Summon an ender dragon with a custom UUID
/summon ender_dragon ~ ~ ~ {NoAI:1,UUID:[I;0,0,0,0]}
Summon an area effect cloud with the ender dragon as owner
/summon area_effect_cloud ~ ~ ~ {Duration:2000,Radius:5f,Owner:[I;0,0,0,0]}
Right click the area effect cloud with glass bottles
→ ❌ You will notice that you get a dragon's breath item
Linked issues
relates to
Comments

Good point. I have resolved this report as "Invalid" now because it seems to be consistent with the latest Creative mode changes, i.e.:
Player keeps glass bottle
Player receives at most one dragon's breath
Area effect cloud radius is reduced (similar to using an empty bucket removing water/lava)
I don't know if this should be considered a bug based on what it is now. You do get honey bottles on creative, you can get fish in a bucket on creative you can use a bottle to get water on creative, and Mojang has fixed bugs that allow these things to happen on creative