If he has been sick 4 times he probably has a sore tummy. You might well find he doesn't want food. He won't come to any harm, honestly. Neither will a small amount of dry toast soldiers to nibble do any harm.
The Annabel Karmel recipe book I have recommends BRAT for poorly tummies - I think it's an american thing. B is bananas (alkaline so settling, I think) R is rice, A is apples and T is toast. Apparently those things are safe. If mine are poorly, I tend to do dry toast (or with a bit of marmite for the one who likes it) and avoid dairy.
Yes Kemble I think dairy should be avoided, I know if I feel a bit unwell I don't want cheese/milk... just wonder if he will even settle without it? We'll see how he goes with food throughout the day I guess.