All you need is 1 cup water and 1 cup sugar.
In a small saucepan, bring sugar and water to a boil; simmer until the sugar is dissolved, 3 minutes. Remove from the heat and let cool completely.
This recipe makes about 1 1/2 cups. To make a richer syrup, use 2 cups of sugar instead of just 1.
You can make as small or as large a batch as you wish and store it in the refrigerator in a well sealed bottle for around 6 months.