OK. A Styrofoam coffee cup, often doubled up, with an added Styrofoam lid makes a fairly good calorimeter. The losses can be determined, and its suitable for mild reactions, like melting ice or the heat of reaction for iron and copper sulfate. Styrofoam won't let you burn, a foodstuff, to completion. Just review the diagram -- how will you make these parts, without actually making a bomb calorimeter?