There is a popular brand of garlic tablets in GB which are obtainable from Potters Herbal Supplies of Wigan. These tablets are reputed to reduce flatulence and known to cure bad breath in dogs. Since I used to work for a firm that made them on behalf of Potters, I can state with confidence that the main ingredient is medicinal charcoal, and I believe that it is this ingredient that reduces flatulence and improves dogs' breath, rather than the garlic, although this is probably very good for you anyway. I suggest feeding the farter with the aforesaid garlic tablets. If not available try to get charcoal tablets. Since charcoal is not toxic, try holding the bugger down and feeding him with the whole bottleful at one go. Even if it does not work, the experience might stop him from regarding the matter as humerous.