What role does glycerin or sugar play in bubble formula?
From: 

https://www.scientificamerican.com/article/bring-science-home-best-bubbles/


  The solution with only water and detergent probably made smaller,
  shorter-lived bubbles compared to the solutions with glycerin or corn
  syrup. Bubbles burst when the layer of water molecules between the
  detergent molecules evaporates. But Glycerin and corn syrup form weak
  bonds with the water molecules and slow down the evaporation process,
  thus improving the life span and durability of the bubble. Glycerin
  makes stronger, longer-lasting bubbles, but corn syrup is often
  substituted in bubble solutions because it is cheaper. Can you find
  other substances around the house that can be added to water to make a
  bubble solution? If you try products such as shampoo or liquid hand
  soap, you can check their ingredients to see what might be helping to
  make the bubbles form.