Currently (as of April 2017 and update R41) there is no Stamina Healing Potion in Creativerse anymore that would instantly restore Stamina, and Stamina Regeneration Potions have been changed into Speed Potions lately.
Alternatively you can cook different types of Food at the Cooking Station that will increase the maximum Stamina of your player character, like Corrupted Soup, Pie, Chizzard Pot Pie, Corrupted Pie, Corrupted Sandwich, Melon Pie or Melon Sandwich.
The "Pro" update provides your player character with permanent double your (maximum) Stamina on all Creativerse worlds from 50 to 100 points.