
Lager is a beer fermented cold with bottom-fermenting yeast, clean and crisp.
Light, clean and carbonated, so almost any pale beer fills the slot. What a swap moves is the yeast note and the strength, and in a long drink neither was usually the point.
Pale ale
Pale, carbonated volume with a fruity yeast note on top, and in a long drink the difference reads as a touch of sweetness.
Alcohol-free lager
Everything but the alcohol. In a long drink that was rarely the point, so the swap changes the strength and barely the taste.
The name is the method: lagern is German for storing, and the style is defined by a cold, slow fermentation with a yeast that works at the bottom of the tank, followed by weeks of cold conditioning. That is what strips out the fruity esters an ale yeast throws and leaves the clean, dry profile behind. In a drink that cleanness is the point. Lager lengthens and carbonates without adding a flavor of its own, which is why a Michelada works on it and would be muddled by an ale.
Opened beer loses its fizz quickly — use it fresh.