ensuring a steady flow of caffine for crew is simple. As a stage manager, I assume you have at least rudimentry instant coffee making skills? That is the first way.
The second way:
Buy a slab of softdrink - I work in AUD, so adjust accordingly - at the moment, I can get 30 cans of coke for $14.95 (on special) that is under 50c a can. I place these cans of drink within the fridge at the venue (I have never known a venue not to have a fridge) and I ask for $1 a can - just a round number any way. Something that covers the cost of the cans, and a little bit extra. Current vending machines in Australia charge about $2 a can of drink, by charging half that, we double their potential caffine intake and some people who would not be willing to make the $2 sacrifice for caffine may decide that it is damn cheap for the convenience and buy big.
Non theatre related, but in my year 12 (last year of school) we wanted a way to make lots of money by the end of the year so that our end of year bash would be completely covered by our raised funds - we were having a booze up the day before, and then going to a caberet restaraunt that night. From the first day of school, we sold cans of coke like that to people within our year level, and through an underground network of brothers and sisters of year 12's (the school council had baned the sale of coke from the canteen that year). We covered the booze up and caberet, and had money to spare, in a school of 500 students. We bought the cans for 50c each, and sold for $1. We had about 200 regulars, and as such raised about 8 grand through that venture alone. So it may just give you a few extra cents to go towards the afterparty ;-)