Q.What Could Be Put on a Plant That Would Kill It Within 24 Hrs
I believe my angry neighbor could be sabotaging my tomato plants because my dogs bark in the early hours. My plants were healthy one day and within 24 hours dead and shriveled up. The other plants next to it are sharing the same dirt/soil and sunlight and water. What could have been poured on them to make them die so quickly (i. e. a chemical like acetone or gas)? I’ve been told those could have caused it.

Seems like if someone was up to "no good," they would destroy all the plants, not just one. Pull the plant and look at the roots - could be underground activity by voles or some critter that had lunch.