Using herbal teas, spices and vegetables in a smoothie is helpful to boost antioxidants and offer antiviral properties. It also helps lower the sugar content and calories. Try out different flavor and color options to give your immune system the nutrients it needs to defend itself against viruses like vitamin A, C and K. Teas to try are hibiscus, lemon balm, rose hip, dandelion root, green tea, white tea, rooibos, chamomile, and nettle. These are available in tea bags or bulk teas at most health food stores including Table Market and some grocery stores. Avoid herbal tea blends that are artificially colored or flavored.