I picked up a pack of Kenco Millicano 2 gram sticks to take to college with me because the coffee at the college doesn't taste great and is €1.50 for a tiny cup, so I was wondering in your experience what would be an acceptable volume of water for this mass of coffee?
Those sound like single-serving packets; they are probably intended for a single "cup" of coffee -- somewhere between 150mL - 250mL (5 fl. oz. - 8 fl. oz), depending on how strong you prefer your coffee. Volumetrically, instant coffee is usually on the order of 5-10 mL (1-2 tsp) coffee powder per cup, and this sounds like it's about the same.
I'd suggest starting with 150mL / 5 fl. oz. and try it. Add more water as necessary. Or, in the event that you like it even stronger, use less water next time. For a strength more like mass-market coffee, you might get up to 350mL cup (10 or 12 fl. oz.).
Aren't there directions on the packet or box? Seems like there should be. If so, I'd use those instead. :)