They could certainly do without all the added sugar in drinks and foods, but if the food doesn't taste like what they're used to, they'll stop buying it, so they'll start adding artificial sweeteners to maintain the sweetness level. Or else cut down on the added sugars, and instead add concentrated (and possibly dried, granulated) fruit juices to everything to maintain the sweetness level.

Salt - that depends on the individual. Some people truly are sensitive to it, but I don't think cutting down on the amount of salt in prepared foods is going to make much difference. The consumer can still add salt to their meal. (not to mention that excessive carbs in general is much worse for your cardio vascular health than a little extra salt)

Since sugar and salt aren't going to be taxed for home use, the consumer can just fill up their salt shaker and sugar bowl more often and add more sugar and salt at the table... probably even more than is being removed from their favorite foods.