OK,  a very simple one.

1. 1/2 30cl bottle fanta
2. 1/2 30cl bottle sprite
3. Juice from 1 fresh lemon
4. Fine sliced fresh cucumber - 3 or 4 circular cross cuts
5. 1 Tort, Cherry red
6. Dry Ice large cubes


method.

Place plenty ice in a large glass mug. Squeeze one fresh lemon and pick all seeds from juice. No need to sieve.
Add cherry red on ice, then fill with equal portions of fanta and sprite. Add lemon juice and stir. Add cucumber slices into drink, place one slice on edge of glass mug.
Insert straw and serve immediately.

You may add some whiskey, vodka or gin if you prefer alcoholic Chapman. Enjoy.

there are other recipes of mine for Chapman served my guests everyday.

...

Hope this is still useful to you. Fruit cordials either cherry or strawberry flavor are used to give the cocktail that fruity taste. TORT refers to a measure used for spirits what we refer to as a SHOT for gin or whiskey. The tort glass is sold locally in most glass ware stores.
Alcoholic cocktail or Chapman depends on choice. Like Gin and juice.