Jones soda bottles (all washed and labels peeled off)
medium size corks (I got them at Hobby Lobby)
sand (play sand or any other natural color)
thin rope or thinker twine
hot glue gun and sticks
funnel (to pour sand in bottle)
After all your bottles are cleaned out and completely dry, pour a bit of sand into the bottom of the bottle. You can do as much or little as you like, I did about a little less than an inch or so. Next roll up your invites super tight so they have room to fit in the mouth of the bottle and tie one end of the rope around it. I wanted to go with a treasure map look for my invites, and found these super adorable ones for sell on etsy here. Or there are lots of different ways you can make your own. Another way I did for my son's friend party was done by printing the party info onto a tan piece of cardstock in pirate lingo (like "Ahoy Matey" etc.) with some cute pirate font and burned the edges of the paper for a weathered look. Those also turned out pretty cute. Either way, you can't lose!
Anyway, after you tie your invitation squeeze it in the bottle and leave some of the rope hanging out of the top. Cork your bottle. Then wrap the remaining rope around the cork and hot glue it. This is so when your guests pull on the cork, the invitation will come out too, instead of having them try and tip the bottle upside down and pull it out with their fingers. Ta-da! You now have a super fun and easy invite that your guests will enjoy as it sets the mood for your big pirate adventure!