This is a cheap, easy, and flexible recipe for making invert sugar for a variety of uses in this case, I make it and backsweeten a hard cider.
The recipe, to make just over 300mL invert sugar:
187.5mL filtered water
227g sugar (can use any type, from table sugar to very dark sugar, depending on desired color and flavor)
.5g citric acid
Mix in covered flask or pot, bringing to very gentle boil for 1030 minutes. Can go longer if looking for extra Maillard reactions and flavor development.
Let cool and use for desired purpose.