not good. somebody actually tried and lived to tell the tale:

https://en.wikipedia.org/wiki/1999_Russian_apartment_bombings#Ryazan_incident

Pinyaev guarded a storehouse with weapons and ammunition near the city of Ryazan. Together with a friend, he entered the storehouse to see the weapons. The friends were surprised to see that the storehouse contained sacks with the word “sugar” on them. Pinyaev and his friend were discouraged, but didn’t want to leave the storehouse empty-handed. The two paratroopers cut a hole in one of the bags and put some sugar in a plastic bag. They made tea with the sugar, but the taste of the tea was terrible. They became frightened because the substance might turn out to be saltpeter, and brought the plastic bag to a platoon commander. He consulted a sapper, who identified the substance as hexogen