How do I clean sticky residue from iPad charging ports?

Two iPads both appear to have gotten some gunk of something or another off of my pencil adaptor. The tiny adaptor fell into a trash can in a coffee shop. Both iPads were then attached to the same charging cable that was used with the adaptor. There was a delay of several hours prior to second iPad being in contact with this charging cable. Which leads me to believe that some dry coffee residue may have gotten into and interfered with both ipad’s Charging capacities. They both only charge when cables are half way plugged in to iPad.

Could I potentially clean both iPad ports with cotton swabs and rubbing alcohol or something? Im guessing simply waiting for an Apple scheduled appointment would be wisest.