Here's my (totally non-serious) plan. Make a new rule that for any food to be eligible for food stamps, that industry/manufacturer will have to lobby to justify its eligibility. Obviously the soda industry will spend tons of money on ludicrous claims, and the whole wheat bread association will barely need to expend any effort.
Then, congress turns around and says "Haha, fooled you. The industries that sent the most lobbyists to DC are banned."