Warm drinks like tea are good, as long as it does not make them sick and cause choking; do not give if they are fainting. It is better to heat the body core first rather than put them in front of a fire.

Physiologically correct but alcohol, as a sudden shot of brandy for instance, gives an initial illusion of warmth, and may thus inspire a seriously chilled person to physical activity, and hence the generation of heat. Further alcohol is detrimental.

Huh! Good to know. In old romance novels, if the heroine had gotten lost in a snow storm, or some such danger, the hero would always warm her up with a glass of brandy. Oops!