nurse a drink
To consume a beverage, especially alcohol, rather slowly, either as a means of conserving it or to avoid getting drunk. I spent too much money and got drunk too often when I would go to bars in college, so I've learned to just nurse a drink or two when I go out nowadays.
nurse a drink
Consume a drink slowly, especially in order to conserve it. For example, He nursed one drink for the whole evening. This idiom alludes to holding a glass very carefully, as one might a child. [c. 1940]