The only way to make Mountain Dew glow is by adding some type of glowing agent, such as the contents of a glow stick. Mountain Dew does not contain the necessary chemicals to facilitate a glowing reaction.
The glowing that occurs in a glow stick is caused by a reaction between hydrogen peroxide, diphenyl oxalate and a fluorophore dye. Hydrogen peroxide reacts with diphenyl oxalate to activate the fluorophore dye to create the flow.
Mountain Dew does not contain diphenyl oxalate, a vital component of the reaction. There is no substance other than diphenyl oxalate that will work to activating the glowing effect. The food coloring in Mountain Dew is not a dye that can be made to glow using a chemical reaction.