Gummi bears contain sugar, and this can adversely affect your dog's system. I'm glad he threw up afterwards, but besides the water, did you see any of the gummi bears in his vomitus? I'm hoping he got rid of them or most of them. Had he drunk a lot of water after eating the gummi bears? If so, this may be why he vomiting so much liquid. Otherwise, he was just vomiting stomach contents, and if he hadn't eaten any of his own food shortly before the gummi bear ingestion, he only had liquid to throw up.
I'm glad to hear that he has an appetite and has eaten his dinner, plus he's acting normally now. Watch for any more vomiting, and if this happens, he should be evaluated by the vet, ASAP for supportive care and an anti-emetic to stop the nausea/vomiting. As a precaution, a vet visit tom'w, by his regular vet, would be a good idea, if you don't need to have him seen on an emergency basis, tonight. The excessive sugar ingestion may cause a laxative effect, so watch for any loose stools, and also, due to your dog's age, it might adversely affect his pancreas, leading to a diabetic reaction. Older dogs are more prone to develop diabetes, so his blood glucose should be monitored.
I hope he continues to act normally and will be fine!