Fill 2 pitchers 1/4 full with ice. To each, add a layer of orange slices, a few lemon slices, and a layer of cucumber slices. Repeat the layering. Pour in the Pimm's and Sprite, dividing between pitchers, and mix with a long-handled spoon. Poke mint sprigs and leaves down into drink. Divide drink among 8 tall glasses, with a few slices of fruit and cucumber in each glass, along with some mint leaves.
Notes: Persian cucumbers are small, thin-skinned, virtually seedless, and very tasty. They're sold at well-stocked grocery