Chewing gum

Yes indeed, folks, there was chewing gum in period. It's novel, yet revolting.

Get yourself some wheat seeds, quite a few, stick them in your mouth, leave them for a while, allow the enzymes in your saliva to break down the proteins and starches a little, and eventually you will end up with a blobby, chewy, carbohydrate mass which you could consider to be Medieval Hubba Bubba (although, I'd really hate to try blowing bubbles with this stuff).