Pour gelatin over the juice and leave to swell.
Pour sugar over water, bring to a boil and hold for 3 minutes, stirring constantly.
Remove from heat and immediately add the swollen gelatin. Stir until completely dissolved.
Pour juice with gelatin into the molds and put in the refrigerator until completely solidified. To make fruit marmalade easier to get out of the mold, lower the bottom of the mold for a couple of seconds in hot water.