I printed my end of the year gifts on sticker paper so I could just cut them out and stick them on the bags. You could also print them on normal paper or cardstock and staple, tape, glue, or tie them on.
Here's the link to buy it from my TeachersPayTeachers store ($1.50):
You can attach them to any spicy treat-- Hot Takis, Flamin' Hot Cheetos, Dentyne Fire or any other cinnamon gum, dragon's breath rock candy, Fire Balls, etc. I ordered Hot Takis and Dentyne Fire on Amazon Prime, and they were at my house within 1-2 days.
Here are links I found for the cheapest ones on Amazon (referral links):
Hope your students (and you!) have a summer vacation that's lit.