Question about Canon GI-56BK Ink Bottle

Hardly possible without using force. It seems to me that the lower part of the cap construction is "glued" and only the actual cap can be opened by turning it. This means that only a small opening with a kind of non-return valve is available. With some tinkering, it may be possible to construct a small funnel that pushes the spout protection downwards. But due to the small opening, filling becomes a game of patience and the "mess" is almost certain. Either way: I generally advise against using third-party ink with the Maxify GX series. The original bottles are inexpensive and the number of possible prints is quite close to the manufacturer's specifications: black 4500 - 5500 copies, colour approx. 12,000 copies, depending on the user profile. So the page costs are (very) low! But in the depths of the Internet/Youtube you are sure to find a more suitable tip.