Anything as long as its not your chart with your finger on it screwing with your navigation.
Personally I don't have anything or maybe an A4 knee board from tescos if IFR. Coffee bad idea unless its in one of those cups that self seals and you have to press a lever to get any out. Only down side of them is they are a bitch to get out of the footwell if they fall down there. I knew a pilot that got some quite nasty burns from sugary coffee spilling on his lap.
Some sticks don't get in your way and for me are at thigh level. Others you could use as a brush handle. There is no issues touring in a robin. And from experence you can fly both with a kilt on
