use
fun MultiPlayerGameMode.useItem(player: Player, hand: InteractionHand, yRot: Float, xRot: Float): InteractionResult
MultiPlayerGameMode.useItem but with custom rotations.
Vanilla net.minecraft.world.item.BucketItem.use ray traces through net.minecraft.world.item.Item.getPlayerPOVHitResult, which reads the player's current rotation. Keep that local prediction aligned with the rotation carried by ServerboundUseItemPacket.