I’ve come across the question really recently, because my players have now an Inventor as a HQ upgrade, and it grants chemicals to them.
Since one of my players knows about chemistry (as a player, not as a character, but the character is Sherlock Holmes-like and knows things as well), they asked about flammable, pitch-like semi-liquid in a flask. I allowed it, but I told them it’s not even like a hand-made grenade, it’s just flammable and will help them putting something ablaze if needed. Short version: I homebrewed a kind of “explosive” to fit the creativity of my players. It cost nothing since they had it from their Inventor.
I wonder how they mean to use it.