Choose a Method for Adding Lemon. Pour lemon juice into the secondary fermenter. The most straightforward way to brew lemon beer is to add a small amount of lemon juice to the beer during secondary fermentation. Some of the sugars in the lemon juice will undergo fermentation, which will add complexity to the beer.
You can add the acid in the form of lime or lemon juice if you simply add enough fruit. Although many brewers cringe when people want fruit in their beer the result is quite refreshing. I personally enjoy wheat beer with lemon and light lagers with lime.