My dog is vomiting food and mucus. Is it bloat? When to see a vet?

Oh no, poor Bandit! I certainly understand being concerned about a GDV (where the stomach twists), but when dogs are suffering from that, they are unable to vomit despite trying. In a weird way, it's good he is able to vomit and has food in it. Other signs you would see include restlessness, enlarged abdomen, pacing, anxiety, and looking at the stomach a lot. Because I can't see him in person, i can't rule out the chance of a GDV, and if you are very concerned about it, certainly take him into a vet immediately. Otherwise, you can choose to monitor him and take him into a vet immediately if he starts trying to throw up but can't, or shows any of the other signs I mentioned above. Should you choose to monitor him, I can give you a home remedy to try to see if that helps. Withhold food for 12-24 hours, then feed a bland diet of boiled white meat chicken (no bones) and white rice in small amounts several times a day for a couple of days. Then slowly add back in his normal diet. If the vomiting continues in the absence of food, he vomits the bland diet, develops diarrhea, stops drinking water, starts vomiting water, or becomes very lethargic, he will need to see a vet right away. I hope this helps!