Bubblegum are consumables that are found in small yellow boxes, with the product name clearly shown against a blue background.
Behind the scenes
The following is based on unverified behind the scenes information and may be inaccurate.
In Fallout 2, in Redding, The Chosen One can tell Sheriff Marion "I'm here in town to kick ass and chew bubblegum - and I'm all out of gum." This is a quote taken from the movie They Live.
End of information based on unverified behind the scenes information