Blacklight glowing foods...found some

deviled eggs glow greenish. if you put slices olives and some red food coloring you can have bloodshot eye looking eggs.
grated parasan cheese kinda works,
hard candies of a few kinds work really well. think cheap assorted.
as for the tonic water this worked GREAT! take some flat tonic water and pour into a ziplock sandwich bag, probably a cup or a little more, let out most of the air and seal. get a few of these and place around the base of a large bowl or something and kinda crinkle them up looks cool as hell in the blacklight.
sorry its late but we didnt discover this til our party.