I'm going to buy beer for my daughter.
Why would you buy beer for her? Can she not buy some herself?
I'm the man of the house, it's my job to make sure she has her beer
As long as your daughter is of legal age to drink alcohol, there isn't anything wrong with purchasing beer for her if she  enjoys drinking beer. It's good that you show consideration for her by taking the time and effort to go out and buy something that she enjoys consuming.
She is home from college and I have not seen her in a while so it is my treat.
It is good that you are doing a favor for your daughter. You can bond with her over the beer that you purchase for her.