if and when I find myself In that situation, I usually follow the rule that some calories is better than no calories. You can make up for it tomorrow.
I've been off coke and shit like that for so long now, that if some very strange reason I "attempt" to drink one, I feel dehydrated before I've got through half, I just feel like I need a heap of water. Not sure if that is even a good thing or not but I can just feel the sugar and caffiene not doing me good and just craving water.. I don't go anywhere with out water, I hate feeling remotely thirsty and water has now become the only thing that will quench that may be slightly phsicological I'm not sure