Color accuracy would dictate you fill them with milk. Still, some sort of spirit would be a far better fit for either the Stormtrooper Decanter or Stormtrooper Shot Glass. Both are based on the authentic and original Stormtrooper helmet molds created by Andrew Ainsworth back in 1976 when his industrial design studio was commissioned to make props for a then unknown sci-fi movie. The Super Flint Glass decanter boasts a 750ml capacity while the shot glass actually holds far more than a standard shot at 150ml (a touch over 5 fluid ounces). If Imperial troops use these to throw back then that explains their aim.
Find them at The Fowndry – roughly $15 (shot) to $28 (decanter)