I suppose you could give them a few drops, but nectar is very high in sugar and typically would be for lories or humming birds that have that type of diet naturally and require higher cal count for energy. Personally I think conures are hyper enough already LOL. Why not just give some fresh fruit, that way they get fiber and such too.
Presently have six Greenwing Macaw (17 yo), Red Fronted Macaw (12 yo), Red Lored Amazon (17 y.o.), Lilac Crowned Amazon (about 43 y.o.) and a Congo African Grey (11 y.o.)
Panama Amazon (1 Y.O.)
You're better off giving whole pieces of fruit that they can eat, like some orange slices or apple. They get the fiberous material, as well as entertainment out of eating it. Like everyone else has said, nectar is just sugar, like plain fruit juice is. There are some edible flowers you can give your birds (like dandelion) which they do enjoy as well.