Preheat oven to 475°. Rinse almonds under cold running water; thoroughly pat dry. Very finely grind almonds and 1 tbsp. of the orange flower water together in a food processor, about 5 minutes. Transfer to a bowl, add glucose syrup and 1 cup of the granulated sugar, and mix with a rubber spatula until thoroughly combined. Dough will be dense, tacky, and slightly crumbly.
Transfer dough to a nonporous work surface, like marble or stainless steel, and knead until a ball forms, about 5 minutes. If dough is too dry to form a ball, add 2–3 drops of orange flower water and knead until dough holds its shape.
Divide dough into 10 equal pieces and roll each piece into a 6 1⁄2" rope. Knead and pinch dough together if it cracks and breaks apart while being shaped into ropes. Cut each dough rope in half crosswise, then shape each piece into a 1 1⁄2" ring and smooth out cracks. Moisten your hands with a little water if dough begins to stick to them. Put cookies on a parchment paper–lined cookie sheet at least 1" apart and bake until lightly golden brown, about 5 minutes. Transfer cookies to a cooling rack and slide cookie sheet under rack.
Put remaining granulated sugar and 1⁄2 cup water into a small pot and boil over medium-high heat, stirring often, until sugar dissolves, 3-5 minutes. Drizzle syrup over cookies, then liberally sprinkle sparkling sugar on top. Set cookies aside to let cool completely and dry. Cookies will keep in an airtight container for up to 10 days.