You have to measure what you are pouring if you want to save money on drinks. Everyone loves a generous drink, but when you are trying to make a profit, you cannot be giving away drinks for free! See this image? That is all you need to know! Beauty!
Also have a sharpie at the bar, and have them write their name on their cup before pouring the drink. Then they can bring this cup back each time, thus saving you money on the cups.
Stay away from buying coolers – although it is nice for people to have some choices, you don’t make as much money on Coolers than you would a Beer or mixed drink. Save the coolers for home parties when entertaining a few close friends.
Lastly, if this is a Fundraiser, DO NOT buy all expensive brands. People will be happy with whatever you are serving. Do not buy super cheap brands too… just buy middle of the road brands that will be crowd pleasers.