There is nothing more refreshing than a lemon. The citrusy tang of it's juice can add flavor and freshness to almost anything, be it drink, food, or scent. The acidity if lemon juice can even be used to lighten hair, skin, or as a mild antiseptic.
Historically, lemons were venerated as an antidote for poison. The famous Roman emperor Nero drank copious amounts of lemon juice to, supposedly, prevent himself from being poisoned from his food. Placing poison in food was actually quite common in ancient Roman times.
In witchcraft, the lemon is a sacred fruit of the goddess, like the pomegranate and the apple.
Rituals and spells of purification and renewal can benefit from the use of lemon juice or lemon peel, especially in incense blends, offerings to the goddess, a libation, charged moon water, or as part of cakes and ale. A good example of this would be using lemonade as a summertime esbat drink during ritual.
So the next time you smell a lemon, think of the Goddess, and how you can use this sacred fruit to purify yourself, your surroundings, and your spirit.