With Kizaru's current characterization and moments, it's highly unlikely he gave Luffy the food. Him getting smacked by Luffy surprised him, so it seems he was actually going for the kill against Bonney and Kuma.
It seems he's simply conflicted about his duty, but still puts his job above his own interests and desires. It's possible Luffy simply stretched to get some food himself, if that's what Oda goes with, it may come off as underwhelming, but after Luffy disappeared then was found eating more food with no indication of outside help, it's possible he made the grab for food himself then moved to a more suitable location to get more.
Regardless of how Luffy got the food, I seriously doubt Kizaru pretended to still be shaken by Luffy's attack but was really giving Luffy some food then got up to stop Bonny and Kuma's escape just to pretend to try and kill them for the sake of letting Luffy saving them. Seems convoluted, could've just stayed down or pretended to be focused on wrecking the Straw Hats while Kuma escapes with Atlas. I just don't think he's secretly helping.