Oh the poor little mite, that must be so horrible for him, being sick every 10 minutes will mean that he is probably dehydrated, and vomiting that often may mean that his diaphragm and the muscles around his ribs may be very painful by tomorrow.
I presume that you are encouraging him to have very small sips of water frequently, and have you any Dioralyte that you could encourage him to sip? If not, some flat full sugar lemonade, and (if he likes salt) a little dab of salt on a damp finger might help too, but please don't give him any salt if he is not able to keep any water down.
When he starts to feel hungry, you can encourage him to have more lemonade - or full sugar Cola if that is his "treat drink" - and offer him cut up small amounts of dry toast, spread with a thinnish layer of jam, but obviously no butter yet. Hopefully that will be a good way to get his tummy back to keeping food down, and if he does keep that down, some mashed up banana could be introduced next, or maybe some chicken noodle soup. Obviously introduce the food in small amounts to start off with, and keep anything fatty, or fried, as the last things to introduce.
I hope that he is feeling better very soon, and that neither you or his brother get it. Hopefully your ill son has only been using a particular towel to dry himself with, and that it is kept where neither you or his brother could accidently use it.
If this either does not clear up very soon, or he gets it again in a few days, then he needs to see a doctor. I presume that you have washed any towels, bedding and clothes that he used a few days ago, as you went along, and as soon as he seemed better. 💐