The stimulant effect of caffeine and other caffeine containing drinks such as soda reaches its peak one to four hours after it is consumed, so steer clear of it from mid-afternoon.
Drink caffeine-free herbal teas, such as chamomile, orange or lime blossom or valerian just before bed or keep to plain warm water.
Having a large meal late in the evening can also interfere with sleep, so eat at least three hours before retiring. You can have a small snack just before going to bed to avoid night-time hunger if necessary.
Drinking a warm, milky drink just before you go to bed might help too, such as hot chocolate. Dairy products are rich in the amino acid tryptophan as well as calcium, both of which may boost levels of sleep-inducing substances such as serotonin and melatonin.
Avoid alcohol but if you must take some do not exceed one unit and take lots of water. Stress can weaken your immune system so take a multivitamin and probiotic to boost your immunity for the next couple of weeks.