Prepare 2-3 glasses to pour apple jelly mixture into. The number of glasses you need will depend on their size. Try pouring the apple juice into the cups beforehand to see how many you will need. Account for foam at the top. Pour about a quarter to half of a cup of the apple juice into a medium bowl and sprinkle the gelatin over it. Set aside for a few minutes to bloom the gelatin. (optional: stir 1 T of sugar into the remaining apple juice) Heat the remaining apple juice until very hot, and pour over the bloomed gelatin. Mix gently with a whisk until melted. Nestle the bowl in a larger bowl of ice water, and stir gently until mixture has cooled down. Remove from the ice water bowl and whisk vigorously to create foam. You want about 2/5 of the mixture to be foam. Pour into cups and top with the foam. Place in the refrigerator for a few hours to firm up. Do not cover with plastic wrap, as it will stick to the foam.