Then yeah, the waiting on the vet sucks but is the best plan. He may need an anti-nausea med. Call them if the email hasn’t been answered by a reasonable time (say after 4-6 hours of their posted opening time today.) Emails are less time sensitive than a phone call.

Food can be swapped or supplemented with plain baked or boiled chicken, rice, and puréed pumpkin (NOT pie filling!) if they’ll take it.

My vet gives a probiotic any time she prescribes an antibiotic now, it’s called Fortiflora and it’s a packet you sprinkle over their food. Maybe ask about something like that?

My dog taking chemo also has a standing prescription for an anti-nausea drug. If it’s this constant for your dog, you should ask your vet about options for the next couple of week.