If you own or have owned a C5, you are probably frustrated with the lack of a decent place to put a cup or bottle without having to fight it while driving. It's one of the biggest interior complaints you will see or hear. There are several solutions for it that I will highlight here quickly.
My favorite is this ring that slips over the cup holder cover to create a taller holder for your cup. Found online on Facebook at Corvette Clips. $20 shipped to your door, and you can pay $4 to have anything printed on it. This picture has Corvette added to it. The business owner actually prints these out on his 3d Printer.
Corvette Mods has this version for one or two cup holders. Priced at $39.99 Found on Corvette Mods web site.
Here is a $55 option also from Corvette Mods.
There is this waterfall option as well, but just for the Coupe.
In any case, drive safe with a cup holder that works! It's a small cost to improve your safety.