1. Turmeric And Milk
According to the Ministry of AYUSH, golden milk or milk with turmeric is one of the best ways to boost immunity and enhance our body’s natural defence system. Since there’s no cure for COVID-19 developed yet, preventing the infection by our strong immune power is the best way to deal with the situation.
According to a journal Frontiers In Microbiology, curcumin in turmeric is very effective against the human respiratory syncytial virus (RSV) that causes respiratory tract infections in humans. It also prevents the duplication of RSV in the nasal chambers so that the virus doesn’t get transferred to the lungs.  Another study says that curcumin in turmeric inhibits property which is effective against SARS-CoV. 
2. Tulsi And Kalimirch
A decoction made from five herbs; Tulsi (Holy Basil), Kalimirch (Black pepper), Dalchini (Cinnamon), Shunthi (Dry Ginger) and Munakka (Raisin) makes for the best immunity booster decoction, as said by the Ministry of AYUSH. The decoction is recommended to be taken once or twice a day.
Tulsi is said to be an ayurvedic solution of all illnesses mainly due to its antioxidant and antimicrobial properties. Chewing its leaves help release flu symptoms and the problem of the lungs such as bronchitis. Piperine in black pepper is a potent antioxidant while cinnamon possesses anti-inflammatory and antimicrobial properties against infection. Dry ginger is known to everyone for its immunity-boosting compounds  while raisins are packed with vitamins and minerals to fight against viruses.
COVID-19: Immunity Boosting Tips For Indians By Ministry Of AYUSH
3. Cardamon, Pepper And Lemon
According to a study, lemon juice has an immunomodulatory effect due to the presence of protein components in it.  The high amount of vitamin C (a natural antioxidant), folate and potassium in lemon juice helps boost our immune system and keep us healthy. Also, the antiviral and antibacterial properties of this essential vitamin wards away all the infectious diseases.
Black pepper and cardamom are one among many herbs that have potential immunomodulatory effects. A study says that an extract solution of black pepper with cardamom has anti-inflammatory and antitumour properties. It helps enhance the natural defence system of our body and regulate inflammatory responses against many infections. 
4. Ashwagandha And Mushroom
Grifola frondosa, commonly known as hen-of-the-woods is a type of polypore mushroom grown mostly at the base of the trees. They are rich in beta-glucans which is an active immunomodulator. On the other hand, ashwagandha is known to increase the antibody response against pathogens and help fight diseases.