those are not sugar ants.
those ants love aphids. they farm them, moving them from plant to plant. they defend the plant from other predators while the aphid larvae feeds off of the life giving force of the leaves. They prod the larvae and keep them awake eating, stimulating them any way they can.
All the while, the ends, the prize, is seeping out the larvae asses and the ants drink all night and day like unshaven sexually confused vikings at the ballet theatre