For our project class we did a powerpoint on smoke grenades. The formula is actually just very simple. Heating KN03 and sugar together just mixes the reactants together (but you still need heat for setting it off). The sugar and KN03 compounds just break off into water and C02, which causes the smokes (water is steam because it is really hot). The leftover oxygen is for boosting the burning. You need a fuse for this though (we used gunpowder. The gunpowder we used was 75% KN03, 15%Carbon, 10%Sulfur). Here is a picture for the gunpowder. Mix well after measuring it out.
And here will be a video I got from Youtube using a formula like ours, just different measurements.
