Tried to drink 2 potions very quickly.
Drank first potion and then switched quickly to the next right before the animation finished and it used up both the potions but only got 1 effects and only got 1 bottle.
Also works when drinking two buckets of milk.
Thank you for your report!
We're actually already tracking this issue in MC-849, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.