I feel like it needs more lemon zest adding somewhere. The zest is where all the good lemony taste is - juice just provides sourness IMO.

BTW, the ingredients list says soda water, but the instructions mention grapefruit soda. Could be interesting…

Very refreshing summer drink. I suggest to use the japanese method for gin tonic. Put the glass in the freezer and use very cold ingredients. Start with the lemon juice, syrup on top then a very sparkling soda and last the ice. If it is not mixed well use a spoon and move it carefully up and down.

Honestly disappointing. The sugar syrup is at the bottom, the lemon juice above, then soda on top. It's deconstructed and an unpleasant experience. Probably shaking the first two ingredients is best.