First, we need to check what version are you playing, and where did you get it from?
If you play right from the start, this will be the items the bartender has to offer. Please make sure you play from the beginning and talk to the girl at the bar. In order to "buy" the tequila, you need to "right-click" on the item, or just "drag-it" to the right panel.
Then talk to Sandy again.
We can see from your screen capture that you "haven't bought" the tequila yet, you still have $2500.
If you need further assistance, please let us know current version your playing and if you downloaded it here or somewhere else.