I just switched the milk for a snack and drink, there was no fuss.
If you're afraid of ditching cold turkey why not prepare a milk but leave it out of sight whilst you offer the solid snack and only bring it in if he fusses for it. If that happened say 2 or 3 days running then go for a gradual wean of reducing ml per day but you could well find that he doesn't ask for it at all and your fears are just that, fears. I often found changes were more difficult for me (due to anticipation of difficulties) than they were for DS.
I would just offer a piece of fruit, or a couple of crackers, or bread sticks, or some left over veggies a drink of water and see how he goes.