Flush Mount Cup-Holder

71mm inner Diameter
60mm deep

Should hold:

German 0,5L Glass Bottles ("Fat and Slim Versions")
Austrian 0,5L Glass Bottles
0,5L EU Drink Can
0,33L EU Drink Can
16 fl oz Party Cups

and of course everything smaller (250ml Can is wobbly but doesn't spill)

The drainage hole in the Bottom is big enough for a finger in case you drop something in that you can't grab from the top.

Drill 80mm hole in desired mounting surface and countersink it until the cupholder sits flat.
Max thickness of plate is ~40mm
Use impact resistant material !