I found a thin travel cup that fits in the front holder snugly. Only really good on the freeway when I'm not shifting alot, otherwise it goes in the rear holder.
I actually use a cup I bought for my E28 which has a really wide base and shaped like a triangle that sits well on the dash. Nix sharp turns though.
I installed this armrest as a comfortable armrest and as that it gets an 'A'. Cupholders are 'C-"/Canholders gets an 'A' and Storage is a 'C'.
1999 540it - Jet Black/Sand Beige, style 5 rims, Zionsville Cooling kit
1984 533i - Schwarz/Schwarz, 17" style 65 reps
1997 318ti Sport - Schwartz II/Schwartz Anthratz, style 68 rims
1995 318ti Sport - Schwartz II/Schwartz Anthratz, style 27 rims
1994 325i Sedan - Bostongrau/Tan
1991 318ic - Schwarz/Anthratz Stoff
1985 635CSI - Schwartz\Sand - Sold
1984 318i - Champagne/Tan, Stock - Sold