The only prescription food that is low enough in carbs in the Purina DM. The rest of the brands don't even get low enough with their diabetic formulas wet foods.
That said. When they need a special diet, sometimes they need a special diet. We adjust, we test more, we watch for bad signs. If it is just for stomach upset, the flagyll will probably clear that up on it own without a change in diet. A couple of days isn't too bad. When we've had to feed or medicate with things we'd prefer not to, we watch the numbers and if we see them heading into bad territory we re-evaluate the priority of the med/food vs keeping the BGs down.