one thing i have found in the past, if its gastro or ecoli, if you get to the stage where they are keeping food down, and are starting fluids as well, when they start feeding, mix in a tablespoonfull of natural yoghurt into the food, it helps greatly to promote the good gut bacteria and assists in re balancing the gut back to normal.
All advice on here seems on the money to be fair, and the manuka honey part is 100% correct. A mate of mine 's dog had a flesh wound, took to vets, stiched up, dog pulled stitches out asap, he started dressing the wound with manuka honey, he told me himself,