Seems like useoncreature()/useitemon() doesnt work correctly with fasthotkeys enabled (atleast with item "mug of mead", id 2880, u can buy it in svargrond tavern)
useoncreature(2880, $self)
useitemon(2880, 0, ground($posx, $posy, $posz))
________Code:12:17:38.168 Event 346 issued. Type: Use Item On, ItemId: 2880, CreatureId: 56042218 12:17:38.168 Event 346 started. 12:17:38.168 Event 346 finished successfully. 12:17:41.646 Event 347 issued. Type: Use Item On, ItemId: 2880, CreatureId: 56042218 12:17:41.646 Event 347 started. 12:17:41.646 Event 347 finished successfully.
edit. probably it doesnt work, because filled and empty fluid container have same id