Things like toluene, hexane, alcohol, ammonia hydroxide and xylene all produce odors. Make sure the little washer is under the black caps on the bottles.
The ammonia/acetate reagent (RE-2313) does produce an odor that is similar to vinegar and maybe somewhat sweet
To alleviate the problem….Odors are from vapors and they are generated faster when the hotter weather starts in. Keep the kit cool.
Also if they open the kit every day and use it it might lessen the odor intensity.