Sippy Cup? Seriously though, I noticed that the theater seating we looked at had a removable cup holder that slipped down between the recliners. It looked pretty slick and even looked built in, but again, it was removable. You might check with GD to see if these are available.
Kelly, after looking at the set up of the 385TH, other than mounting cup holders to the slide wall, I would suggest a portable console that many pick-up truck owners use that have bench seats. That way you have two cup holders, an arm rest, and storage for remotes or whatever.