Fortify

befæste

(to increase the defences of (an army, soldiers, etc.); to put (it or them) in a defensive position)

berige

(to increase the nutritional value of (food) by adding ingredients)

forstærke

(to give power, strength, or vigour to (oneself or someone, or to something) — see also strengthen)

spidse

(to add spirits to (wine) to increase the alcohol content)