Both Sweet Veil and Aroma Veil's effects apply in Single Battles.
Sweet Veil will protect Swilrix/Slurpuff from falling asleep.
Aroma Veil will protect Spritzee/Aromatisse from Taunt, Torment, Encore, Disable, Heal Block, and Attract.
The only reason that Flower Veil doesn't apply in Single Battles is because the Florges family is not Grass type so the ability doesn't work on them.
Source: Experience
